TIf,E E'ATRTTGIIg EXPEATSUED When the Fairlight CMI was released seven years dgo, both the machine and its software represented a significant step forward in the application of computer technology to music. Today, the Fairlight is used in the rnaking of popular music the world over, as well as performing an important role in the field of musical and technological education. Despite this, very few people are fully aware of what the CI}II does and how it does it. Jim Grant, who's been working with one for a number of years at the London College of Furniture, has decided to rectify matters by writing a series dedicated to explaining the Fairlight's workings. Part one appears below.
E&MM AUGUST1984 efore the Fairlight'sappearance, most computer music systems werethe perogativeof mainframes and their contributionto the world of 0r,1il8Nn everyday music was slight. Kim Ryrie (the Fairlight'sfather) and his Australian PIIDE I INDEX colleaguessoon changedall that, how- rnbL < DISK DONTROL ever and their inventionis now used in rNbL J KEYBDHRDCONTRclL almostarea of music production,to the PRGE 4 IIIIRI'1ONI C ENUELDPES many people extent that appreciateits PIi|jE 5 I,IEUEFORIlEENERBT I ON sound without realising that they're f nl-'L b I,IHUEFI]RI'1IIRfiI,I I NC listeningto 'musicby numbers'. However,despite its widespreaduse, I|1IRLI[HT PBriE 7 cc|NTR||LPFRRIlETERS thereare relativelyfew Fairlightsin general PRIJED S|JUNDSRIlPL I tI|] .100 circulation- less than in the UK - PFDE S SEUUENDER and to see one in actionat close quarters PH6E FI ffNffLOGINTERFHIE is a realtreat. Herein lies the rationalefor PBl]E [, COI'IPOSER this series of articles.What does the PFEE D l,IHUEFORHDI SPLFIY Fairlightdo? How does it do it? And PBriE L DI SK L I BRFRY what can the averagemusician do with I l,l.I PrirlE R RERL-TI IlE CD14P|]SER it? u3 , t5, Rl , l l TNbL 5 SCREENPR I NT Hardware I.JSERNFI14E , JIll DRRNT To take deliveryof a Fairlightleaves l@t your bank balanceempty and your living room full. The hardwareconsists of a CentralProcessor Unit (CPU),one - or optionallytwo - six-octavekeyboards, a 011flfftiD' typewriter-styleQWERTY keyboard, and a VDU with added lightpen.ln addition, DISK, EXEIlPLE FREE SPHCE. 536 thereare some long connectingleads, a USER. JIT'1GRflNT LIBRffRY NO. 8 floppy 1 INUENT .IN I6 STIDK C|] Systems disk driveand a box of 2llitrIlErm t7 ItiuENT .S0 disks containinglibrary sounds. 3 PRELUDE,IN I8 PRELUDE.SO 4 UIUFLDI ,III I9 UIURLDII.SO 5 BfiSSGT .UC ?B LOCUST .RS 6 BDD2 UC 2I PBGEI .PX Software 7 CBELLO(][}UC E2 PFGEz .PX 8 GRNGSR UC 23 PFGES ,PX A foolproof system of connectors- S STICK .UC 24 SYHTH .PC and a quick glanceat the manualon the 1B STRI'II D UC 25 SYNTH . PT 11 IfrNN UC 28 BFSSD .SS part of the user- ensuresthat the Fairlight T2 ERSSGT CO 27 CNTRL .SS can be powered up in no more than five 13 BBDz.. .C0 28 SN3 .SS minutes.The VDU 14 CBELLOOO.CO29 TUHEl ,SS displaysthe expectant I5 GRNGSR .CO 36 TUNEz ,SS message'CMl READY',while the CPU hums quietly:there are three fans pulling IlULTI CIiNDEL air throughthe innards,keeping 500 watts TRBNSFER DELETE EUERY clt r EII tlcL power of dissipationdown to an accept- !.qgH$I .,-l|:| .tvee:-ln$IRU|]1ENi .,, ,ye| l, ..:i,,r,e , 24. . abletemperature.... voices'BDD2 STICK BFSSGT STR|4ID lnsertingthe Systemsdisk in the left- T handdrive (Drive 0) resultsin a faintclick as the stepper motors engage. The l@ operating software is loaded as a series of 'fetches'- each section of program loaded pulls in the next section.When this process has been completed,the user is faced with the Index page. See Figure1. Here lies one of the Fairlight'smost powerfulfeatures. The whole system is menu-drivenand the differentoptions correspond to different VDU displays and sets of commandswhich are entered Com'irter from the alphanumerickeyboard. Each rcthsb@rd option is referredto as a Page. A Page has one or more files resident9n the Systemsdisk whichare loaded when the Page is selected.Page 1 is the Index
Menu itself (Figure 1), while Page 2 Address managesthe files stored on the disk in bus the right-handdrive (Drive 1). These files are user-created, and there are seven differenttypes, as indicatedby the suffix afterthe file name.These are as follows: Cmlfol NAME.VCis a voicefile occupying about crrcurlry 2OkBytes.lt holds waveform data (1610 wovelorm RAM and extra informationregarding looping dio signol and so on. oulpui NAME.CO holds control information such as portamento,vibrato frequency and depth. 28 AUGUST1984 E&MM channel cards perform this function autonomously.The computersection of the Fairlightpasses parameters such as pitch,vibrato, portamento rate and loop- ing pointsalong its data bus, and once sheet, 2 IfIIiIIEIIIIE and types these have been received,the channel 3 Ffim SPRCE on disk card outputsthe sound until the para- 3. lfnfilfli$ number meters are updated. 3 EfiffilflIn tiles {t4ULTI & CBNCEL) Overallpitching of the CMI is deter- flllffiE disk, usen or f i ]e nenret mined by a systemclock residenton a 4 EIIfII command soecialcard knownas the Mastercard. c EN:III|IE instnument on voire files We'll be referringto this on numerous f ml!fiflIn instrument f iles occasions over the next few months, 6 I[ll|ifflE voice f iles since it holds the circuitryfor a good b ]m:filfln sEquence f iles many of the CMI's functions.A 34MHz 7 |lJifllfll somnrend oscillatoris onboard,and this is divided 6 If#IIEiIfE cor'mahd and fed to the individualchannel cards. I nFffiff:dmftfmlfi pnotect i on the RAM clocking 18, ImmLEf0 orr mtsster k eybosrd It's from this clock that it mfiil:Im shortcuts rates- and thus keyboard pitches - are generated.The whole instrument can be toucn sny l0X r^rith LIGHTPEN or type, n(set) tuned by scalingthe masterclock. uherE: n = sneel touch lIffi or tvPe' HI ( netur n ) EE!tr4 Page2 Commands Lookingagain at Figure2, there are severalcommands at the bottom of the display.TRANSFER allows files to be copied from one disk to another,using Drive0 as the destinationdrive. This is TRfiNSFER FILES TO BNOTH YPE. L I GHTPEN, essentialfor creating backup copies of T,file(retunn) (select files) importantmusic and/or sounds. DELETE or
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B6 SEPTEMBER1984 E&MM the basisof the usertwiddling the con- nel allocationand keyboardmaps. unique sound, and therefore the maxi- trols and stabbing the keyboard. Fair Figure5 shows a typical displaywith rhum number of notes that can be play- enough: of all our senses,the ears are eight separate voices loaded into the ed on the keyboard with any single by far the most acute.Yet if we consider CMl. RegistersA to H are groupsol one sound is one. This is indicatedby the all the electronic music equipmentcur- or more of the eight Ch.annelsand corresponding'NPHONY'. lf a single rently available,the most user-friendly 'NPHONY'is the numberof notesthat eight-notepolyphonic vorce is required, instrumentshave graphic displays,per- can be played with the sound held in a only RegisterA will be activeand Chan- haps in the form of panel legendsand Register.A quick lookat Figure5 reveals nels 1 to 8 will be allocatedto A. The LEDs or liquid crystal display. Despite that there are eight active Registers, active Registersare mirrored on Page 2 the fact that sight is a very poor quali- eachholding the voiceindicated. In this so that they can be loaded with sounds tative sense, it can be of enormous case, all eight Channelcards hold a from disk. The Fairlightwill flag an error psychologicalhelp in our field.Basically it boils'down to: 'lf I can see it. I can TEUHPET f4ulrE, 4 understandit.' I,IFUTFDRI'1TI I i;PLRY :J.r D^ r-\ STEP.l E 4 r d.Bu,^^ u There's no doubt that the Fairlight's visual presentation is founded on this premise.Each displayPage is graphic withoutbeing ostentatious, and PageD, the voice waveform display,is a prime exampleof this. TypingPD followed by a RETURNon the alphanumerickeyboard will resultin a displayof the typeshown in Figure 1. To appreciatethe signifi- cance of the display,we must delvea little deeper into the workingsof the CMI. Rememberthat voice informationis held in 16K of RAM on each channel card. To simplifymatters, the CMI div- ides the memory (and thus the wave- INIlEX form) into 128 sectionscalled segments. 0l'll,lffNIr, Each segmentconsists of 128 bytes,so the waveform comprises128 segments multipliedby 128 bytes to give 16384 fi I I lIr!a ie. 16K.This savesthe musician 5 2 i Sr I Cll bytes, t' 3 ) BH5:,r.iT handling unwieldy computer numbers D { i STRI,II II 1 when dealing with the waveformRAM. E 5I'STF;14ID2 The display shown in Figure1 is a F 6 r c8ELL00q psuedo-3D voice G 7 ) TffNN representationof the H P I rlHNr:SF called TRUMPET.Each line from left to right is a segment, and the foremost segmentrepresents the beginningof the sound. When a keyboard note is :l ,l',1i{::rTEF: FITr::H, l?U E .!JLffUE si:FLE, t(lT pressed, the CMI reads out the RAM a'j informationsegment by segment from the front to the rear of the display. There are two display formats,A and B, and a numberof optionswithin each type. Figure1 is in formatA, and seg- ments1 to 128 are shownin stepsof 4. Figure2 is againformat A, with the end segment number 32 and steps of 8: thereforeonly five segmentsare shown. OHHfiND' Format B gives an oscilloscope{ype display,but with each segmentslightly SHXY Lg25 above the precedingone. Again,there SNfiRE 886 are a numberof displayoptions. Figure BDRU14 ?,48 3 shows TRUMPETsegments 1 to 128 ORGtiN BAVJ in steps ot 2, and Figure4 segments1 to 64 in steps of 8. AlthoughPage D is purelyfor display purposes and does not support any sound creationcommands, it's still an invaluableaid. At its most basiclevel. it 3 .I,lFSTER P I ICH' I28 answersthe ouestions'where has the 6 .SLFUE SCFLE, l?r-:; sound gone?' and 'is the waveform V <.UU zero?'. ragel\^ 5 Page3 is anotherutility-type display Page.lt dealswith voice tunings, Chan-
SEPTEMBER1984 E&MM OMPUTERMUSICIAN message if you try to open another to eachoctave. As the C[/l is a music- quitean elegant solution since'music by Registeror increasethe NPHONYbey- ian's instrument,it supports two six- numbers'requires lots of numbercrun- ond eight.A simplerule applies: the sum octavekeyboards called the Masterand ching, but the other choice, and one of the active Registers times their the Slave.Using the maps,it's possible whichis becomingincreasingly popular, NPHONYmust be lessthan or equalto to create eight differentkeyboard con- rs computrngconcurrency. In a basic eight. figurationsby choosingwhich sounds CMI system,there are four micropro- Figure6 shows anotherexample of will play on each octavewithin a key- cessorsof the 6800family. Two of these the Registerallocations. Here, another board. The Master and Slave can be are in peripherals,ie. one each in the set of voices has been loaded.so the linked(as shownin Figures5 and 6) to music keyboardand the alphanumeric NPHONYand Registersare configured any map by changing the Selection keyboard,and this meansthere can be differently.Although the Registerand numDers. several independentprocesses being NPHONY settings may seem a little Theinformation presented in Page3 is executedconcurrently. confusing and limited,the exact con- knownas an Instrumentfile. The file can The microprocessorin the alpha- figurationis determinedentirely by the be savedon the userdisk and is given numericscans the keysand passesthe musician,and changescan be effected the suffix NAME.IN.When this file is data to the music keyboard when very quicklyfor evaluation. loadedit will pull the specifiedvoices requested.At the same time,the music into the CMl, allocate the Registers keyboards are scanned for pressed automatically,adjust the tuning and notes,key velocitiesare calculated,and Keyboardsand Tuning spread the sounds across the key- the controlsliders and switchesread. Any voicecan be tuned in increments boards.Instrument files are a usefully At the right-handend of the Master of plus or minus one hundredthof a quick way of bringingthe CMI up to a keyboard is a calculator-stylekeypad semitoneup to t6 octaveswith crystal playablestate with 'preset'voices and and alphanumericdisplay used for rapid accuracy. Scale allows the Western tuning. loading of voices in a live situation. temperedtuning of 12th root of 2.00 to rt I Music keyboard information has the be changed to any other macro/micro 11arcware highestpriority of all data in the CMl, tuning,eg. for quartertones, you simply At thetime the Fairlightwas designed, which respondsinstantly to the packets changeScale to 24th root of 2.00.Pitch the microprocessorwas consideredto of data sent flying down the cables at is a master tuning control which can be a medium-to slow-speeddevice. To 9600 Baud. varytuning of all the loadedvoices by a increasethe power of any computing Well that about finishes off our des- quarter of a tone in 256 discretesteps, system, designers have two basic criptionol the utility-typedisplay Pages- to bring the CMI in tune with other choices. In caseyou're wondering what the Mode instrumentsif necessary. Oneof these(the Synclavier approach) settingon Page3 is for, don't worry: all The KeyboardMaps each consistof a is to basethe instrumentaround a dis- will be explained. keyboardnumber (1 to 6) followedby six crete logic minicomputer,thus utilising Next month, the controls on Page 7 lettersindicating the Registerassigned the raw speed of logic chips. This is andsampling on Page8. r OMPUTERMUSICIA TIIE T'ATn.LTGIIT EIKPEATTUED Partthree, and a discussionof how the CMI samplesa sound and why its own particularsampling techniques are employed.Ji* Grant A t last we'vecovered enough of the CMI resultsin a short sound when the samole is than can be looped is known as a Segrpeit /.\ basics to concentrate on the more played on the keyboard,and this becomes Here lies the crux of choosing a suitable , \ interestingsound creation Pages. Now, shorteras we ascendthe octaves.To over- SampleRate. lf we attemptto loop a Segment the single feature that characterisesthe come this,the Fairlightallows sections of the or group of segmentsthat doesn't contain a Fairlightin manypeople's minds is its abilityto waveform RAM to be read out repeatedly (or wholenumber of cycles,the 'ends' of the loop sample natural sounds: this aspect is dealt looped)as the key is held down, thus sustain- won't join up withoutcausing a suddenlumpin with by Page B, and is surprisinglysimple to ing the sound.The smallestsection of RAM amplitude.Choosing an inappropriatesample USE. At the rearof the CMI liesa selectionof line UDIr-'E, I 0t'll'lliNIr, I'rH Fi I l'1 and mic inputsto suit most applications.That :1 about takes care of the hardware.because :lr-rl_lHDtHl'lFL I HrJ everything else is dealt with by software. Typing 'S' or touching 'Sample' with the SRI'IPLE FTIiTE Zv I EB Hi EHI,IPLE LEUEL c::. lightpeninitiates the samplingprocess. After a FILTER LI:II,I I TR I GI]EF; LEUEL : second or so, the Display box shows the FILTER HIGH E TFIII-;ijEFI TIELB\. E tli sound envelopefor quick monitoringof input Iit'lFFrEigr:rFi I'FF levels (see Figure 1). lf all is well with the Keyboard Maps on Page 3, the sampled SfiI'IPLE soundwill be playableon the musickeyboard. far good. what the So so But are other IIISPLFIY functions for? Well, some of them are self- explanalory. Sample Level is a software- based volume control and can be used to attenuatesignals that exceedthe input range of the Fairlight.Unwanted frequencies can be reiected by using digitally-controlledhigh- pass and low-passfilters: their cutoff points areset by FilterHigh and FilterLow. The actual Figure1. circuitrylives on the ubiquitousMaster Card, and takes the form of switched resistor Iiltt:, networksusing the much-lovedCMOS 4051 Ul'1l(lli{It, RTUNE chio. l40DE, 4 Whenevera signalis convertedto a stream I,]FUEF|]RI'I! I 9PLHY of digitalnumbers, it's necessaryto bandlimit it to one half, or less, of the Sample Rate. Statedsimply, this means that we musthave at least two samplevalues of the input signal's amplitudefor the highestfrequency present. lf this conditionis not met. the informationthat the sarnplingprocess has captured is not sufficient lo reconstruct the original signal without frequency distortion. This type ol distortionis known as 'aliasing'and is both extremelynoticeable and rather unpleasant. The CMI guardsagainst 'aliasing' by incor- porating tracking filters controlled by the SampleRate.
SampleRate Figure2. Althoughsampling itself is verysimple, and impressive results can be obtained very | I ll IrE:i UiJIUE. 1 r-rtlt1HflIl- quickly,it's well worth the troublespenrjing lt LTt-tt{E llDIrE, .{ some time adjustingthe Sample Rate to a I l,lHrllEFr-1Frl'l tr MLx'i. valuethat suitsthe pitch of the input signal. l-t IiFtfii FIFJ'1FiT + 11Ir ::iE t:; ::r? 5TEF, I
imporrantaspect of theCMr that obtiges us ro payattentron to thecorrecr^:T?1"^ r.u^t:^- ffili,iii?Fr ,^ [l:liili.#, The number of original samples taken is --rli./ llii',:;ttlj,, :-. r' .,' fixed and equalsthe length of the waveform [,1]lll'*ni:L1:----.=l--ts RAM,ie 16334.The faster these samples are taken,the shorterthe durationof the sound L''Figure3. becomes (althoughthe fidelity increases).This
86 OCTOBER1984 E&MI I 1 OMPUTERMUSICIAN l rateresults in a dreadfulglitch which increases conect clockingrates requiredfor digital{o- shortlybefore the signal to be sampled and at a rateproportionalto the pitch playedon the analogueconversion when a keyboardnote is usedinsteadof thesignal itself to triggerthe keyboard, lf the sample rate is almost right, a pressed. However, for the duration of the samplingprocess. Trigger Delay can then be one-segment loop produces a sudden slight samplingperiod the CPU grabs Channel 1, used lo define the precise point at which pitch shift, and waveform crests and troughs and forces it to produce a streamof pulsesat a samplingwill actuallybegin. This is extremely 'drift' laterallythrough a PageD display.This is frequencyof 128times the samplerate shown usefulfor soundswith a gentleattack such as shown in Figures2 and 3, where a drift to the on Page8. This is suppliedto the ADC,which slow strings. right (sharp)is caused by the sample being set resides on the Master card, and once the Lastly,the Compressoris a softwareswitch too high and a drift to the teft (ftat)by it being samplingprocess is finishedthe CPU restores which controls a hardwareoption. Basically, too low. Channel1 to its originaltask. this turns the conversionprocess into a non- Figure4 showsa sound which is in tunewith TriggerLevel is the amplitudethreshold at linearsystem, thus enhancingthe dynamic the system and therefore loops perfectly. At which the sampling process is triggeredto range.The electronicsuse the same type of the other end of the scale, if the sample rate is begin.When the Samplecommand is given, circuitryas that in manyanalogue companding totally wrong the display becomes a hopeless the system waits until this level is reached systems. However, very few Fairlights are jumble (Figure5). The relationshipbetween a before proceeding.Once the threshold has fittedwith this option as it can havea strange whole numberof cycles and each segmentof been exceeded, it's possible to delay the effecton the commandson Page 6. waveform RAM is also the relationship conversionby usingthe TriggerDelay, which Well, that about wraps it up for Page B. required for a visually coherent display. Thus hasa rangeof 0-65533milliseconds. This can Thereisn't roomthis monthfor a discussionon samplesthat look good will inevitablysound be especiallyuseful when sampling from tape, Page 7, so we'll have to leave that for next good, too. for example,as a tone burstcan be recorded month. r Now, if all this sounds rather complicated and you're beginningto wonder how anyone IiLEi; I gets anywhere near choosing the corect trlJ8ilIl ITUIIL .l sample rate, then take heart. lt's all in the help l,lSuEFrtPilIr I ::FLfri, pages for Page 8 - see Figure 6. A useful sample rate table is included,and with a little practice it becomes quite easy to arriveat the conect setting within the space of a few trial samples. ADC The actual analogue-to.digitral conversion is accomplished by a 10-bit converter, even though the CMI is an eight-bit machine.Only the top eight bits of the sample values are stored, while the two LSBs (Least Significant Bits) are ignored.This improves the linearityol the conversion, which means that the signal step size required to cause a conversionvalue to change by one LSB is fairly constant over Figure4. the range of the ADG. / The relationship between the amplitude of the input signal and the sample values I't I generated is linear. When the signal level 0l'll'lFNIr' JTUNE t'100E' i changes by a given amount inespective of the I,IITUEFcJRI'IDI SFLRY absolute value the conversion code always F|:lRI'18T.F 4 32 STEF'12 changes by the same amount. This is where the Fairlight differs from most other sampling machinessuch as the Emulator.That uses a non-linear conversion method (called 'companding')which allowsmore codesto be generatedfor small signal valuesthan for large ones. Whenever a signal is represented by a finite range of numbers - in this case f255 (eight bits) - two things suffen noise and dynamic range.The noise is only heardwhen a sampled sound is actually being played through a DAC, ie. the ADC and DAC are not in themselves inherently noisy. Making sure that the peak ol the input signal causes the maximum ADC code to be generatedensures that most of the noise is masked by the volume of the signalon playback. The Displaybox in Figure1 is an invaluable aid in this respect. Dynamic range, on the other hand, is a measure of the range of different amplitude values that the ADC can handle. In a linear system, this is directly related to the numberof bits used in the process and, roughtyspeaking, SffI,lPLE RIlTE9 the dynamic range of the sampled signal is noie +gvts -Evr -tE: ,"'i 6dB times the number of conversion bits. Since the Fairlight uses this gives 14817 29S35 74SS 3?t3 eight bits, 8 E :jB5 x = 15884 TiiEr! I 6dB 48dB dynamic range.Companding c 18744', Er:r7e 4 I FE techniques result in a larger dynamic range 17748r 8r:rlB 44:{5 (about 70dB)forthe same numberof bilsused, r sTss 3337 4EtS but at the expense of greater noise at low tsst2 iig5E 4S7'il signal amplitudes. The reasons for Fairlight's E 2I BSB 1Erg49 5t7'{ choice of a linear converter will become more F 22351 I I I I i, ii,,:,,1 apparent when we look the functions ?3EBB lltr4El SrllF at on I U544 Etr? Page 6. t3t38 EE45 The actual sample rate is very cleverly generatedon Channel card 1. Normally,the onboard circuitry is used to generate the
E&MM OCTOBER1984 6l u..:=;
fi t THE EATn'LTGHT E tr)KPEATTUtrD How the CMI providesfor specialeffects and looping - in a languagejust abouteveryone can understand.Ji* Gra,nl I ast monthwe dealtwith one of lhe activevoice is shown in the top right- resultsfrom its use. The Filteris a lor'.,- I Fairlight's main sound creation hand corner.Other control files can be pass tracking filter resident on each L methods:sampling. The simple act inspectedby pointingthe lightpenat the Channelcard, used to attenuateanv of pointing a microphoneat a sound namesin the displaybox or by typing unwanted high-frequency conten: sourceand typing 'S'on thealphanumeric 'V.n'.where 'n' is thevoice number. present in the voice: the cutoff fre- keyboardtransforms the Fairlight from an Thereare six real-timefaders and five quency is raised by simply increasing expensive computer into a powerful switchespatchable to mostparameters. thevalue. lt's all reallya caseof svrings musical instrument.And the keyword Threieof the faders and two of the and roundabouts- a high filtersettino hereis 'musical'.The ability lo createnew switchesare on the left-handside of the givesa bright realisticsound but often and interestingsounds (or indeed sample music keyboard,while the otherfaders with digital birdies waroling in the them) is not in itself enough.What is (orfootpedals) are accessible vra Cannon- background, while low filter values requiredis controlover that sound and, to type connectorson the rearof the key- suppressany funnies but reduce the coin a popularphrase, the controlmust board. In addition,the music keyboard soundto a dull noise. be real-time.Musicians, of course,call When Portamentois on, each Chan- this control'expression', and it's a par- nel allocatedto the voice produces a ticularlydifficult feature to build into a continuousglide between each nei.,' computer-basedmusical instrument. pitch it is to play and the last pitch Considera typical case in which a played,the rate of note glide being set Fairlightuser might be playingthe music by the Speed control. 'Glissando'drf- keyboardwhile listeningto a sequence fers from Portamento in that the glide pre-recordedon Page 9. Everythingis is not continuousbut chromatic,and running smoothly: the CMI is reading all the notes on the keyboard between sequenceinformation from the disk, sort- the stad and end notes are played. lf ing it out, and sendingthe data to the both Portamento and Glissando are voicechannels to be played.At thesame selected, Portamento takes preced- time,the music keyboard is being scanned ence. 'Constant Time' is a switch for pressednotes and moredata sent to which selects between two types of the channelcards: notes are stolen if glide: when it's turned on, the same necessary.Next the usermay decide to time is taken to travel any musical swell a parlicularvoice by movingthe intervgland the rate of change alters appropriatefootpedal. Here the CMI is ac_cordingto that interval, hence the forced to deal with an asynchronous name 'ConstantTime'. This results in eventin the normalproceedings, so the polyphonic portamento or glissando. pedalvalue has to be updatedconstantly passeskey velocityinformation to the in which the notes arrive at their andthe values obtained used to scalethe prod- CMl, and this can be patchedto Level destinationsat the same time amplitudeof the voice throughoutits and Attackas KEWEL. ucing a coherent chord. With the duration.And if thiswere not enough, the Below the voice list in Figure1 is a switch off, the rate of change remains Fairlighthas 17 parameterscapable of (determined comoletelist of thecontrols and switches fixed by Speed) and the beingcontrolled in real-time. thatare available. This is usedin conjun- time taken to glide varieswith the size It'sthe unusualmulti-orocessor archi- ction with the lightpenand providesa of the interval. tecture of the CMI that enablesit to quick way of patchingthe controlsto handle so many asynchronoustasks vai'iousparamelers: the lightpen is pointed Attacl frll irFF iFpfl h-EYUEL I ooninq r"'b E@m@ Choosingthe correctlooping point of a ::h,:,r,1!:r3n.-r::: ;nii Ft,t!iL'l* p:t,:h*:- i':,r voice wavelorm can make or break a !th t,3n F 3r 3fir*tPr Figure 2. good soundon the Fairlight.Nasty glitches [l,rntr,:I P.:r.inreter Ranq*, F:1,:h can occur if an inappropriatesample rate llLltrE 1, I is chosen or if the section to be looped LI,F r-lll. L-IFF !, .:htr_Fl-: LE(IEL rrl-:'99 | l.: f r-tiTF,Lt-r, spans a naturalchange of amplitude. I I L I LFJ I'lE\r,rEL lmagine trying to loop a percussive NHNP I TID Lt-tt:,J5 t: sound such as a drum. The three loop BTTTiDK 8-16:l:13 LI controlson Page7 providea quickway of EL I S9 NIIO ON,OFF : finding loop, PgRTIiI'lENTIJ OT.I,OFF i the best anda typicalsetting ,]TLL! 8-l!7 c might be as shown in Figure 3. Here I:IJHSTRNTT I TIE OH,BFF .f Control 1 is used to define start point of UIBRIITI IIEFTH 8-I?,7 c the loop while Control 2 sets the length. UIBPIITD 9FEED A-I?7 I LI]DP I]ONTR|]L ON,DFF D Switch 1 freezes the effect of Control 1 LDDP STf,RT c and Control 2 when off, preventingacci- L00P tElrETH S-128 D dental movement of the looping points STBRTSEDMENT I-I28 c once these have been decided.A useful SLUR ON,OFF i 9U5TFIIN featureis that loop parametersare sved 0n,0FF with the voice informationas well as any UUILL: Linked control file, so that the sound is gTEI'IIDI playable even though no performance controls are required. The actual loop Figure CONTROLPRRF}lETERS points are displayedgraphically on Page TONTROL FILE' LOOP CD 4, as shown in Figure 4, where the = horizontal axis representsthe segment HoI'E 4 r:LlggFtiDo 5l,lTcH3 Lri0P CilrRL = ::HTr-HI EXF,= I]FF PNRTFIIIENTO OFF LO|JP STIiRT = IT{TF;L1 number and thereforetime. The loop is LEUEL = KEYUEL SPEEIJ 3{ LIJI]P LN.GTH= DNTRLZ indicatedby the row of highlightedboxes FILIER=8 rlDtiSTTlHE OTI :JTffRT sEG = I graph, under the HarmonicProfiles and DFI'lPIllG = SE UIB IIEPTH = CNTRL3 SLIIR = Sl,lTr-Ha since the voice shown was sampled, RTTf,CK = IF UI8 SPEED = S SU9TFIN = tlFF there are none of lhese present. This Page offers a convenient method of selectinglooping points usingthe light- pen. UOIEEs, EIIII? STICK BB9SGT EI:$T|IIT 'Start Seg' is a powerful expression 9TFTNINS CBELLOBD TRHN GRNGSR control.lt allowsthe startingsegment of the voice to be chosen accordingto a INTRL. SI,ITCH. control value as a new key is played.To explain:suppose we had sampledthe classicsynthesiser filter sweep and play- ItilEti ing the keyboard resulted in a 'fruity' r:rtl l'1F tt Il STRtllIrl HFIRtl0NIC q decay. Using a control fader to set the H0I|E, start segmentwould then enableus to play the synth sound from ditferentparts l of the filter sweep. As the controlwas I i movedfrom segment 1 to 128,the sound \ would beginwith plentyof filtersizzle at J low control valuesbut become shorter I I and moremellow as we startedthesound I I further the (by increasing I down sweep I the Start Segmentnumber). This tech- \ nique can also be used to control-the I PLDT I amount of 'breath' on sampled wind L00p l[l|n I sounds or the amount of bowing on t stringedinstruments. t Next month, page 5 and some revel- I ations concerning the mysterious I 'Mode'. \ r \ I .1 THE T'AIn'LTGIIT ETKPEATTYED Samplingmay be the CMI'smost talked-aboutfeature, but asthis article shows,defining sounds using harmonic information can be just as dramatic. Izmf ' Granta\ J o far we have discussed only one soundsneed lots of numbersto represent antwaveform is visually very similar to the methodof actuallycreating sounds them. realthing, and perhaps more importantly, with the Fairlight sampling.This So what's the use of Mode 1? Well, soundsindistinguishable. aspectof soundformation is probably the calculatinga time waVeformfrom har- However,the power of theCMI liesin its singlemost importantfeature of theCMl, monicdala can be quitetime-consuming, abilitynot only to compute a complex and was cerlainly the focus of public especiallyif the supplieddata is detailed waveformfrom a set of Fourier com- attention when the machine was an- and enablessubtle nuances of soundto ponentsso that it can be playedon the nounced. Horvever,the abilityto specify be generated.However, more oftenthat keyboard,but alsoto computea different sound by meansof harmonicinformation not, only a simple waveformis required, wavelormfor each segment. Every seg- can not only resultin somevery interesting and to calculatetheRAM waveform for all men\ has a unique Page 5 display,so sounds, it's also rather useful in an 128 segments when a short loop is all while a Mode 1 sound has 32 sets of educationalenvironment. that's needed is rather wasteful,to say faders,a Mode 4 one will have 1281The Two display Pages,4 and 5, allowthe the least.There's no hard and fast rule currentsegment number is indicatedon construction of waveformsby harmonic aboutwhich Mode a soundshould be in: thedisplay, and this allows a synthesised data. They deal with exactly the same the choice is entirely the musician's. soundto changedrastically throughout informationbut presentit to the musician However,using a voiceas the destinatlon in different ways. for samplingdalaalwaysresults in all128 Firstof all,though, let's clear up a little segmentsbeing ovenvritten,even if the FBue2 mysterythat's been evadingus for some voiceselected is Mode 1. months - the Mode switch.Actually, this is very simple and is thereforesomething h? of an anti-climax.When a voiceoperates rage ) in Mode 1, only the first 32 segmentsof waveform RAM (4k bytes) are used to Figure1 shows a typical Page5 display. representthe sound.An unloopedMode This page displaysthe harmonicovertone 1 sound will stop at the 32nd segment, seriesas a set of 32 'faders' similarto even though another 96 segments of thoseon a graphicequaliser. Each fader RAM exist. ln order to compensatefor is logarithmicin natureand hasa rangeof shorter note event time as playedon the zero to 255, allowinga good degreeof keyboard, each of the 32 segmentsis control over harmonic amplitudesand looped severaltimes beforemoving on to thusenabling the applicationof a Fourier itsduration, simply the userfilling each the next segment:this maintainsa fairly type harmonicseries. by segmentwith a differentwaveform calcu- constantnet event lengthfor any pitch. As an example, Figure 2 shows a latedfrom its own Page5 fadersettings. Mode 4 uses the entirewaveform RAM squarewave generatedby the CMl,com- ln fact,the technique of usingdifferent (all128 segments of it)and is always used puted from the valuesof Fouriercom- waveformsegments as the sound pro- for samplingsince long, high bandwidth ponentsshown on thefaders. The result- gressesis verymuch the domainof PPG Frgue 1. synthesis.Generally speaking, these pro- gressions are known as wavetables, N X UOICT' I andin the PPG,a soundconsists of a set 0 fl rlFHD, S11UBRE HRRNONI C FfiDERS 11ODE' 1 of 64 waveformsthat reside initiallyin EPROM(they are transferredto RAM on cUK KL NT SEGI'lENT I power-up)which are read out sequentially when a key is pressed.The idea behind this systemwas to circumventthe need forfilters by constructingwavetables that held a set of reoresentativewaveforms of, say,the classicfilter sweep. Unfodu- nately,this results in a veryhard, metallic sound, as the sound changes abruptly 1 r 1 t l l I I I I 22????2??2333 I c J 4 5678 I 0 r 234se7 890I234567890l2 from one waveformto another,slightly differentone. lt's still a good sound,but in the interests PPG have zLt{ 0 c0tlPlJ E of flexibility, chosen to incorporatethe usual VCFs andADSRs as well as exiensive wavetable modulatlon. TheCMI is alsocapable of this forrni,l synthesisto a limiteddegree, using the loop controlson Page 7. For example, ntratrrratra 10Al trtMl' supposewe had filledall 128 segments with waveformsthat changevery slightly as we progress through the waveform 0t'tH8NIt, (see Figure 3). Now, if the loop controls were set up as shown in Figure4 (thisis a I,IFIUEF|jPIlN I SPLRY Page 7 display),moving CNTRL1on the music keyboardwould resultin a different timbrewhen the note was played.Using this techniqueallows for some expressive playing,since the principleis ratherakin to varyingthe filterfrequency control on a synthesiser, the only difference being that the actual timbres can be radically different from one segment to the next. To increase the timbral movement within a sound, CNTRL2can be patched to 'LOOP LENGTH'on Page 7, resulting in sections of differgntwaveforms being read out repeatedly.Since the waveform data is computedby the CMl, it's always constructed so that the waveform fits exactly into one segment, therebyover- coming looping problems. FourierSeries Ftguo4 Well,with all this talk of 'Fouriercom- ponents' and the like, some of you may SI,IEEP 'what's reasonablybe thinking it got to do CONTROLPSRRI'lETERS with music?' The answer,of course,is not much. Only scientistsand engineers CONTROLFILE. I,IR delightin quantifyingthe world which our HODE= 4 IILISSFNI0 ut I L|]|]P CNTRL ON senses seem to handle perfectly ade- EXP = 0FF P0RTFHENT0 |]FF LOOP 9THRT C}ITRLl = quately. However, in order to exprbss LEUEL KEYUEL SPEED a LLlOP LNDTH I = ourselves explicitly and unambiguously FILTER 1l tl0NST TIt4E OFF J tlK I CLb CNTRLT about a wide variety of concepts (some of DFHPING= lAg UIB DEPTH=& SLUR = 0FF which may be abstract) we need to use fiTTffCK = 0 UIB SPEEI]=g SUgTFIN = 0FF the language of mathematics. Fourier analysisand synthesisare mathematical statementsabout somethingwhich is not intuitivelyobvious: the fact that any truly periodic waveform can be decomposed UOIIES, FilNTiiI into an infinitesum of sinewaves,usually called harmonics.Similarly, any periodic waveform can be constructed from the 1:-t45 sum of an infinitenumber of sinewaves. FI The sinewaves have frequencies that are relatedto the fundamentalof thewaveform in such a way that the second harmonic Flgnr,o5. lies at twice the fundamentalfrequency, Fgtre8. the third harmoniclies at three times the fundamental,and so on. The fundamental itself is often referred to as the first harmonic. i'i"i"i Of course,obtaining a reasonablerep- Itl resentationof a desired waveformdoes ilITTI not require an infinite number of sine- ,l waves: more than 16 is enoughto give a good approximation.The Fairlightuses a maximum of 32 harmonics,which enables most waveformsto be synthesisedwith a fair degree of accuracy. Figures5 to 8 show the developmentof a squarewave by successivelyadding further harmonics and using Page5 to compute the resultant waveform.The squarewave doesn'tcon- tain any even harmonics (2, 4, 6 and so on) and we can see that the lower harmonic numbers set the basic square shape while the higher ones fill in the bumps and sharpenthe edges.Even with all the odd harmonics the Fairlightcan compute, the square wave is still not visuallyperfect, but it soundsOK. I E&MM DEGEMBER1984 OMPUTERMUSICIAN TIIE T'ATRLTGIIT E)KP&ATNED Waveforms,lightpens and interpolationall come under examinationin this instalmentof our FairlightCMI GrandTour. Ji* Grant ust when you thought it was safe to open up a copy of E&MM without Along the bottom of the displayare the reading anythingabout the world's harmonic numbers 1 to 32. A small most influentialcomouter musical instru- triangleunder the numberindicates that ment, your intrepidreporter returns from the time profileof that harmonicis being a New Yearhangover with anotheraction- displayedon the graph, while a cross packedepisode. This monthwe look at shows that the proflle has a non-zero the informationpresented by Page5 in a vatue. slightlydifferent light. You'll remember So what does all this mean? Have a that Page 5 held the values lor 32 lookat Figure2. Two profilesare shown, harmonicfaders and computedthe result- one of whichis the Firstharmonic (left to ant waveform for the current segment. rightdownwards) and the otherthe Third (left Youshould recall also that the only way to to right upwards). On receipt of a createa completesound of 32 segments Computecommand, the CMI will fill the was to define the fader levels for each waveformsegments with sound which segmentand compute over the whole initiallyat least,has a strongfundamental waveform; or define a few segments NIIEi; and Fill the harmonicdata to the rest of rl tl |1ri ll tl HFR145 the segmentsbefore computing. lt's not HfiFiI'IONI ROFILES l'lrllrE, I hard to see that this method of creating soundsmay be very precisebut can also be extremelytedious. In a lot of cases,all we needis a wayof tailoringthe harmonics as the sound progresses: harmonic envelopes,in otherwords. EnterPage 4. Figure1 is a typicalPage 4 display,and shows that it's one of the two Fairlight displayPages to be almostexclusively lightpen-driven.The largedark area is in fact a reversevideo image, and pointing the lightpenin this regionresults in an mrlfl FLr:r T arrowcursor appearing on the screenat the currentlightpen position. For those lllttl r lllr !2:rrJ:jl l!i45r I [!:i t1 !:tEt1c" unfamiliarwith the term, the lightpenis now a fairlycommon computer add-on, tr n tr mainlybecause of itssimplicity of opera- I.LEHF, [IILETE itFt-t FF' I-I11 tion.Contained within every lightpen is a Eff fast photoelectricdiode or transistor whichproduces a voltagepulse as the W I llIrEi: |r:rlr:E, I linepasses beneath it. Usually,the pulse r: r:r11 f1 H fl Il HB FI I,1 ::; is squaredup and passedto the video HFiF]11[iHI I: FF]iIFI LEi flnlE' I controllerchip, which storesthe W line numberand positionalong the line in a coupleof registers.This information can then be used by the programmer to initiatepredefined evenls such as plotting a point or executinga command. The Fairlightsystem is no different, except that the video controlleris con- structedfrom discretelogic chips and resides on a single eight-inchboard withinthe CPU. In addition to latchingthe TV co-ordinateswhen the lightpenis L r:rr:r F Irirfll FLrrT used, it generatesan interruptto the processorsto executethe selected task. .!i:i:ji:i At firstglance, the graph area in Figure itsjrlit! 1 looksa bitconfusing but it's really quite tr straightforward:the verticalaxis repre- sentsamplitude while the horizontal shows l: f1 li'fti time and hence the seqmentnumber. MARCH1985 E&MM 'tI l. :)ut degenerates into dominant third rarmonlc. l[rf1l'1Hf1Il triF : rl:It llirrEFI:'F l1 IrI :FL H, t11!_._r{r, _l:j_:,t_!EB_.__:TEF [| . c : ,.lankprofile graph. i"lore About Mode One of the previously mentioned lll_r I l-: llFFrl.': featuresof a Mode 1 voice is the way in HirF;llirllI r-: PF:rtFI LEg l'1[r Ir I which the first 32 segmentsare looped severaltimes to maintain the net event timeof the soundacross the keyboard.In fact, we havesome controlover how long a segmentlasts before everything moves on to the next one, and this is accom- plished vrathe profile. Figure4 shows a harmonicprofile graph with the duration profile indicated by a double line: the defaultvalue is approximately50mS per segment and increasesas the profile is drawnhigher up the graph.This is parti- LUI:IP mfnl rL,: j cularly useful for creating sounds with a EE short click at the beginningof each note, '--t"; .-,-.t.-,.-. I tlt rli lrii suchas thatof a Hammondorgan. Avery el45 *, .l*u :'a:' ;lFi Ii rr:lEr I i ili F shortduration value can be drawnfor the I first one or two segments, and then a C o longer profile for the remainderof the I::LEFF, IIELETE F.E'1ET l'IFr:i r:iJtlFUTE ':r-tlLE It1TEF: F r-'. Ef,ti sound. lf the duration profile is made zero,the sound degeneratesto a Mode 4 Resetcauses a confirmationmessage to contain rapid changes throughout the condition,except that it only lastsfor 32 be printed and also results in Page 4 durationof the sound. segments. being restored to a complete default Incidentally, becoming proficient at Another interestingaspect of Mode 1 condition.Zero isn't quite so drastic,and usingthe lightpenfor drawingcan take a profile. sounds is their ENG This is an resultsonly in the current profile being set lot of practice,so the CMI helpsout by artificialenvelope that's superimposed to zero. Everytime you give a Compute providinga Join Plotselector: when Join on the waveform in much the same waY command, a new energy profile is is active, any two points struck on the principle. as the more usual ADSR But generated.Scale is the opposite: it re- graph are immediately connected by this one's a lot more flexible.When the drawstheharmonic profiles from a modi- a straight line, while fine detail can be Compute command is given, the CMI fied energyprofile. This is not without its drawn by selecting Plot. I imagine that calculates the waVeform segment by dangers, however, as it can result in most of you will be familiarwith the segment and scales the amplitudeso some harmonic profiles being scaled Fairlight'sLoop function by now, so I that it fits exactlyinto the dynamicrange beyondtheir maximum amplitude, which won't go throughit all again.Suffice to of eight bits. The ENG profile is also leadsto clipping.The Fairlight w7l inform saythen that Page4 offersa quick way ol generated(and its shape implied)by the you of the situationwhen it occurs (by drawingthe loop startand length.Mode 1 harmonicdata, but can be alteredby the displaying'Overflow') but is powerlessto soundsare alwayscalculated so that the lightpen to control the amplitudeof the preventit happeningif theScale command waveform fits perfectly into a segment: sound on playbacltr is issued.The only way to recover the the first harmonic does one cycle, the soundthen is to reloadthe voice. second harmonictwo cycles,and so on- A''I'F Timenow to introduceanother conceot Gone are the Bad Old Days of trying to Auxrlary Functrons withwhich some of you may not be overly sample a sound to make it fit segments familiar.lnterpolation is the skillof guess- evenly.All you haveto do now is use any Along the very bottom of the display ing an unknownvalue that lies between old loop to span the sectionsof a wave' Page are a number of usefulcommands. two knownones, and is commonlyused formthat areof interest,and Bob Moog's Clear deletes all the displayed profiles to predictvalues of pointson graphsthat your uncle. from the graph, but they remain active aren't the actual ones originallyplotted. Next month (yes,there's still more to and can be broughtback to lifesimply by When the Interp switch is On, each come),we'll take a look at Page6 which, the programmerselecting the harmonic waveformsegment is computed from a arnongmany other weird and wonderful numberswith the lightpen.Delete, on the mix betweenthe harmonicnrofiles of that things,allows you to splicea sounddown otherhand, merely removes the currently- segmentand those of the next one. The to no more than 16,384thof its length. selectedprofile. The same soft of structure differencebetween the two is subtle,and Ahd you thought a razor blade was appfies to Reset and Zero. Invoking is only reallynoticeable when the profiles powerful. .. r E&MM MARCH1985 TIIET'AIRLTGIIT E)KPEATTUED When a CMI pageis as helpful a source of musicgraphics as Page 5, you can bet your lifeit needsa lot of explaining-sothis month's episode is dedicatedentirely to it.J i,nt()ru,rtt I f you're tryingto createa new sound Iil[rtt,,: lrir T r- C I on the Fairlight,whether it's from r:rl'1 ll H ll Il tl I existingsampled data using Page 8 or lt H| | EF r:rF11 IrF:B!i I ttrj harmonicprofiles generated on Pages4 and 5, you can be surethat Page 6 willbe referredto over and over again. At its simplestlevel, Page 6 is a siatic 'oscilloscope'containing one segment of the waveform RAM. Like Page 4, the largeblack areais a reversevideo image and representsthe regionthat can be hit by the now-infamouslightpen. But unlike an oscilloscope,which acts only like a window on the information,Page 6, in conjunctionwith itscommands and light- ::'TEF F:BTE, pen, behavesmore like a door through iTBFiT which we can directlyaccess the wave- form data. rjlr_rF The ManualApproach Figure1, Regularreaders of this serieswill pro- bably recallthat each segmentconsists hold 5lrE * f llntllEfliJilIl I::FiBFH of 128 bytes,and that each byte can r:: .-r giving tillf,G[m E[i t{ [ f{ T !:::: i r, r, Er, t a rangeof valuesfrom -128 to 127, IiIEf,I[E';,'11i1n -3;1';{ possible a grand total of 256 values.Now, FIEf,ffiEIID :-t:F'p i r' -r il i !F 1 :? we can highlightany particularbyte by [IftMEm rnjr]Ff'-1rnii1 ,:, il iti'::ti':rr positioninga narrowvertical window over I?fjltrro{E[ r.I.3L.'ef 'rr rr nri r:ii I i i 3t i,:'r-l fiirilUfiflfifi :-rri tf h The byte in question, the display area. Effil] ,: ,:,n, n, 3 r;il shown in Figure1, has its positionindi- m[film L-:i ft,Iir .-rr'il cated by P0INT and its value by nt[ilImfiffil'., ilrt t,:,rLl .JPl'r*r 3tl,:,rl L EV E L: thesecan be changedby typing lililI] ,: ,:,ri rlr3 i'ril ,:, in differentvalues from the alphanumeric tifffn ': ri I' 3 n il tlf{iliti ,: i, r,rL, 3 r, '|:l keyboard.So, theoreticallyat least,you IIIIH i ii tritr 3r-r il could type in 128 levelsfor each byte mlffi[i ':,:,rirti' :ti,:l shownin Page6, and repeatthe process nEfitrFEm ,:i,L,r,i 3tril r,r r-, for all 128 Page 6 displaysto coverthe R!roI{#Tl i,-l i, i il Iff,illEnnB ,:i, r,,n-Jritl entiresound, giving 16,384 levels in all. In lifiE : ':,r,ir,,i,r',:] practicethough, such a feat wouldtake t[illfl rilitti,-1 r, an unbelievableamount of manuallabour l![AlffilfffE I r''|:-tl'r'rin+r'i : rr,:l (exactly what much of the Fairlight's Irf::::,,,rr tl', L I r.HTiIii,rr- T'iFE r,rh':t'E softwarewas designedto eliminate)to [[IG 'rr T iFE achieve,and this has led me to wonder whether this feature will be dropped when the Series lll Fairlight,complete ul'lNriflIl l'lriRItltrl with waveform RAM of megabytedimen- r:iir Ufl Ir itil'IFLINC sions, makes its appearancelater this year. ::;HI'lPLERIiTE I 4EjijB 5FI'IF.LELEUEL t5E A more practical approach is, of F I LTEFI LUI,I I TFIIT:GEELEI,IEL t5 FILTEE HILiH .1 TRIII]ER IIELHT u 1,1! course,to makeuse of the lightpen.This tr-rHF'FrEgSuR r:rFF is as simpleas drawingon the backof a bus ticket, but just in case eventhat is beyondthe user's artistic capabilities, the iHt'1FLt J 0 I N and P L0T functionsalso present on Page4 areavailable here, too, to help TII:lFLH\. out with the drawing of geometric snapes. In fact, trying out a few samplesket- ches soon revealsthat waveformswhich look drasticallydifferent may sound sur- prisinglysimilar. Scientifically speaking, this is probablydue to the fact thatas a APRIL1985 E&MM OMPUTERMUSICIAN species,we have little prior experience Ifiii irt: gained It:f I fromour sensesthat relates visual - ''rlllrilri i'18F,I 11I B time domain waveformsto what we perceivein terms of harmonicsor par- tials. :iiI'FLI FHIL 1.1i: F] LEI,IEL 'J :.HI]F'LE :59 But Page 6 waveform-drawingis of FIt.IIi Lr:rt] TF:lr.r:IF,LEIIEL r5 I-ILItF'HII.H TF'II:iL,EF'IIELBI I l'1':, enormoushelp, first because it givesthe 'r-riJFF[:':11F user extensive and direct control ol r_rF i- waveform RAM with one sweep of the hand,and secondbecause the abilityto _ fl tr I t bringabout such drastic sonrc change so simply and visually(almost artistically, It]:FIti,' some might say) is a practicalitylight yearsaway from the sophisticationand complexity of the underlyingmachine and its software.Or to put it anotherway, it makesthe CMI seemless of a beastand more of a pet. Figure4. The PracticalApproach IlJIrtfl Alterationof the displayimage is not ulrl'lFfltl reflectedin the waveformRAM untilthe r:ir:r l_l lj Ir ::iH l\l F, L l il [ F I L L commandis used.This allows the reverse video field to be used as a :iHIIPLE EFITE I qil:lU Hi iBI{PLE LEI.IEL i55 scratchpadarea in which waveshapes F I LTEF Lr_ril I TFtlr:r:;EFLEr.rEL t5 FILTER HIIJH iJ TEI ir:;EF: trELhi' E I'll can be developedbefore they are finally r:Lrl'lFFiEitrJR r-lFF committedto RAM. Lookingagain at Figure1, noticethere are two 'slider'controls similar to those i lil'lP L E on Page 5. These control the segment numberto be displayedand the stepping II ISFLItY ratethrough the entire memory instigated when the commandStep is issued.Also shown are three classic waveforms- triangle,sawtooth, and square- which deposit a perfectly fitting single cycle wave into the segment.The pulsewidth Figure of the square can be varied from 17oto 5. 99% by changingthe valueheld nextto turnedend on end by usingR EVE RS E, limagine N0ISE will be fairlyself- the squarewave symbol. andthis results in the backwardssounds explanatoryto eventhe leastclued-up of that have become familiarto pop music this column'sreaders: it fillssections of followersthe worldover. the RAM with the output of a random AuxiliaryCommands REFLECT is a lesscommonly-used numbergenerator hidden inside the sott- Inaddition to thegraphic capabilities of but if anythingmore interesting variation ware. Funnily enough, the GA I N Page6, thereare a numberof commands on this theme. lt allowsus to olace an command is also used to tailor the that can only be entered from the Fair- imaginarymirror in the sound and reflect amplitudeof the noiseto that of the rest light'salphanumeric keyboard. Figure 2 everypart of the waveformin front of this of the sound... shows the range of functionsavailable, mirrorto waveformRAM behind it. Take a Now, BLEND is a strangelyout of as presentedby the HE LP sheetmenu. look at Figures3 and 4 for beforeand place command. Personally,I think it First off are a f6w utility-typecom- afterviews: the 'mirror'is at segment64. shouldbe on Page4, since its role is to mands.GA I N scalesthe displayeddata Now on to anotherof the seemingly help smooth out glitches caused by by a specifiedpercentage: if the rescaled insurmountableproblems brought on by imperfectlooping points. lt maybe thatto waveformis about to exceedthe ampli- the onset of new musicaltechnology. finda goodloop it makesextensive use of tude rangeof thesystem, the CMI will ask Very often, when a sound has been extrapolationtechniques, and that see- you whetheror not you want to proceed sampled,the beginningof the captured ingas thisis a centralfeature of the MI X and therebyinduce clipping. lf you reply data does not occur at exactlythe startof and MERGEcommands, Fairlight deci- in the affirmative,the commandwill be the RAM, perhapsdue to some extra- dedto bungit on Page6 alongsidethem. dulyexecuted. Meanwhile, the I NVE RT neousnoise pretriggering the ADC. How- However,rather than discussthe re- commandinverts the phaseof the wave- ever, if the effect isn't too severe, a mainingPage 6 commandsin any detail form:this is usefulas a preludeto someof convenientmethod of correctionis to rightnow, I thinkit's probablybest for all the other functions such as MIX, R0 T AT E thesound within the waveform concernedif I demonstratetheir power in MERGEand ADD. RAMto bringthe startin linewith byte 1. the context of a typicaledit sessionin A parlicularlyneat little corirmandis This has the (oftendesirable) side-effect whicha soundis created from scratch, ie. ZERO,which allowsus to createa null of shiftingthe firstpart of RAMto the end. withoutany sampleddata. So, now you voice in preparationfor the AD D com- SeeFigures 5 and3 for anotherrevealinq know what l'll be talkinq about next mand. The entire waveform RAM can be beforeand after month. 'AHIGETTING A BIT OVERDRAWN' H^{M/I/1I!A,..JHINK I'LL START 5AiINUTES LATER AT THE BANK, TIME To Co/YlPoSE WITH A +,'+ RHYTHM,.. A{oTHERANoTHER MEGA-SMASHMECA Ht7 ...ANOfHER A ASTERPIECE SIN6LE. I THINK.' FINISHEDJTHINK I'LL JUST DO .FouR REA^IXESOF TntS ONEJ,1 S /r{EA HEAD- : JUST TR/ING TERL''TE CHI E&MM APRIL1985 THEE'ATRLIGIIT E)KPEATTUED Inwhich we takea lookat the differencebetween linear and logarithmic conversion,and incidentally end up creating asound using the Fairlight's synthesisfaci Iiti es.J im Grant ostpeople involved inthe modern RDDCOIl musicindustry are already aware noDE, 4 of theFairlight's incredible poten- IIRUTFORN D I SPLSY tial as a music prodrction tool. These days, you switch on the television,radio or record player in the almost certain knowledge that a CMI will make its presencefelt somewherealong the line, and when you considerjust how useful its specificationis to studio Ongineersand producers,that's hardly surprising. Even in 1985, there aren't many machines capable of spreading six octaves of sampledsound acyossthe keyboard, and manipulating that sound within user sequencesto the nth degreeof preciSion. But if you're fortunateenough to sit in front of a CMI for any length of time without any production deadlines to lloDE 4 meet, you'll soon discoverthat its creat- nautFoRnDIspLny ' ive power lies as much with sound synthesisas it does with musicproduc- tion per se. Pages 4 and 5 are good examples of this in that they offer the fairly standard synthesis tools of har- monic sliders and profiles,but Page 6, which we introduced last month, is something of a softwareoddity, since it allowscontrol overthe wholewaveform - from a single byte to macro type com- mands such as GAIN, Ii1IX and IIERGE. Now, for any command or processto be really useful in the field of sound synthesis, it must be responsiblefor some radicalchange in thesound struc- 0it18tlD, BDDC0n lloDE' 4 ture that's both intuitive and easily f.BUtFoRn DIsptBy understandable.For example, the VCF of an analoguesynth changes the sounda great deal, and can be simplyexplained and understood in terms of the attenu- ation of harmonics.FM synthesis,on the other hand, also resultsin vast timbral differences, but comprehensionof the processes involved (and their possible results)is a lot more difficult.That's why actuallyarriving at a pre-specifiedsound on sonrethinglike a YamahaDX7 requires so much in the way of practiceand patience - and why so many musicians prefer programminganalogue synths, evenif the ultimatesonic potentialisn't as them directlyinto the samesegments of sinewaveboth residentin differentchan- great. the currentlyselected voice, scalingthe nelsof the CMI: the resultof ADDing Fortunately, the Fairlight'sinternal amplitudeto avoidclipping if necessary. themtogether is shown in Figure3. The configurationside-steps most of these lf you were to A DD all the segmentsinto addition's proportion can be varied by operational problems, and a good ex- another, playing the keyboard would using the GA I N command prior to the ample of how this is done is the A DD result in both soundd being heard action,or by repeatedlyADDing one command.This takes a choiceof seg- togetherbut only usingone voice.Figure voiceto anotherto increaseits amplitude ments from one loadedvoice and adds 1 shows a squarewave and Figure2 a relativeto the comDositesound. lrav r oa< trnMM OMPUTERMUSICIAN onrAilD, fl I xcon mtntmum MSB=1 1111 VoiceWhveform (Triongle) FilD, SYNT0f4 Sl]UNDSRNPLING S8I1PIE RRTE I 4O8O HZ SAilPLE LEUEL 255 FILTER to'l I TRIGCER LEUEL 15 FILTER HIGH 8 TRICGER IEL8Y O NS COI1PRESSOR OFF Figure 4. Linear conversion. SSIlPLE DISPLRY 0111 Figure 8. 0t1l1RND, SYilTor'l SOUNDSBIlPL I NG SRIIPLE RSTE I4O8A HZ SBI1PLELEUEL 255 F I LTER LOII 1 TRI GGERLEUEL I S FILTER HIGH 8 TRIGGER DELRY 9 NS COI1PRESSOR OFF SRIlPLE DI SPLfiY Figure 5. Non-linear (logarithmic) convercion. Figure 9. VUIUL: 11txc0t! FERGCOI'1 noDE, 4 l" waveform is stored in 16K of RAM, in Theterm 'linear'refers to the relationship Linearity which each byte has a binary value that between the actual amplitude and the Now seems as good a time as any to c\oresponds directly to the amplitude of value of the binary number used to explain sornething we've mentioned the waveform at that point. A byte representit. lf all this sounds a bit on the many times in the past but haven'treally consistsof eight bits, and consideringall technicalside (and it ought to), have a discussed in any detail, namely the the possible combinations of these res- quick glanceat Figure4. This shows that differencebetween linearand non-linear ults in the amplitudeof the sound at any zero amplitudecorresponds to binary 0, voice data. As you'may remember, a point being limitedto one of 256 levels. while maximum negatiVe excursion' is E&MM MAY 1985 85 IIRN! PFtl lliflND, TEST ilODE, 4 noDE' 4 I.IBUEFORI,IDISPLf,Y lrf,uEFoRrl DIsPLBY X IIII;T UUILL. I l1l48ND, TEST tlAND. TESTI I'lolE 4 l'loDE 4 rf,uEFoRi DISPLBY ' r,lnuEFoRr,iDIsPLBY ' |-\ representedby 11111111, or 255,and sion process under its commonly used sampled using Page 8 and shown in the maximum positive value is held as name of companding,and it's a system Figure8. lt's pretty clear that the sample 01111111, or 127.Still confused? Well, used by many hardwaremanufacturers ends in a dither of noise. Now, suppose the valueof the Most SignificantBit holds includingLinn and E-mu. we needed nothing more than a short the key. lf that valueis 0, the waveformis So if it's so good, why doesn'tthe CMI percussive strike, and that only the positive,while a 1 gives negativeexcur- use it? Simple. Rememberyour school beginning of the sound was of any sions. Anything else in between is in days when you added log numbers to interestto us. A quick solutionwould be simpleproportion. This form of represen- multiply?Well, this is whatwould happen to turn to Page 6 and ZERO, say, tation results in a ratio between the if theeADDcommand was used with Segments64 to 128, halve the sound, smallest and largest signal that can be sounds held in the form generated by and then MI X from Segment 45 to 64. handled (or in other words, dynamic Figure5: instead of adding the sounds Lookingat Figure9 shows the result- a range) of about 48d8. You might con- togetherto producea mix, we'd get the sound that dies away evenly to a noise- sider that to be not a particularlyimpres- product, and end up with VCA-type free end, much to the relief of all sive figure, since it means that at low effects at low frequenciesand strange concerned. signalamplitudes, the soundis moreor sidebandsat higherones. Which isn't, all l.lERGEis fairlysimilarto MIX - with less surroundedby hiss. things considered,a particularlydesir- one fundamentaldifference. Again, a The fact is, storage (in one form or able state of affairs. form of crossfadeis generatedbetween another) of low-amplitudesounds is a startand end segments,but this time,the l.a' perennialengineering problem, to which l-llxlng previous contents of intermediateseg- the most common solutionis some sort ments don't figure in the result. Quite of noisereduction system such as Dolby. Anyway, enough of the lecture and simply,the segmentsin betweencontain In the digitalworld, and as a directresult backto theFairlight. The MI X command a decreasing proportion of the start of research into digital telephony,a can also drasticallyalter the waveform segmentand an increasingproporlion of ditferentsolution is to use more binary RAM. Essentially,it generatesa cross- the end segment.Figures 6 and 10 (oh bits of the byte to representlow-signal fade between two specified segments yes, very logical- Edl revealall. The MI X levelsthan you usefor the highones. This which must not be adjacent, ie. there and MERGE commands are tremen- is shown in Figure5, in which the lower mustbe at leastone segment in between. dously powerful for splicing together valuesof the trianglewave use up moreof The waveformmemory of each segment soundsof differingorigins and producing the binary bits than a corresponding between the stad and end points con- an even fade from, say, a violin bow increaseat largetriangle amplitudes. The tainsa proportionof the existingwave- attackto a sung 'ahh'. binarydata is now no longerlinear - it's formin thatsegment and that of the end logarithmic.For the waveform to be segment: this is best illustratedby recovered, the data must be passed examiningFigure 6 and Figure 7 for Creatinga Sound througha DAC that has a curve bent the before and after views. Rememberthat So, now that we've discussedmost of opposite way to 'straightenout' the the new contentsof each segment is a the commands available, let's try to sound.I knowall this sounds more than a mix between where you are in the create a sound using everythingexcept littleinvolved, but it doesbring the magic waveformand the destinationsegment. the Fairlight'sPage 8 samplingfacility. dynamicrange ratio up to about 72d8, Thus from Segment 2 onwards, the Thequestion is: am I allowedto usePage whichis at leastrespectable. Only catch waveform simply fades up to a square 2 and pulla soundoff-disk to work with? is, the processonly achievesthis with a wave. MI X is most commonlyused to Well.I've decided l'll haveto cheata bit correspondingincrease of quantisation add a clean fadeout to a sound that because I already have a thoroughly noiseat largersignal levels, though this is decays to noise or doesn't decay pro- marvelloussound called PAN.VC. which maskedby the volumeof thesignal itself. perlyin 128 segments. attacks with the characteristic breath You mightbe familiarwith this conver- Have a look at the percussionsound chiff of pan-pipes. B6 MAY 198s I E&MM OMPUTERMUSICIAN First offoff,, we configure Page 3 to work on the body of the sound itself. look closelyat the differencesbetween generate two voices, one with an Beforeany soundcan reallymake the Figures13 and 14, you shouldn'thave NP H 0NY of 7 in RegisterA to be played gradeas faras aestheticsare concerned, muchdifficulty identifying the variation in on the keyboard,the other monophonic it must have plenty of timbral and amplitude,especially in the sound'sfirst in Register B as a scratchpadvoice. amplitudemovement within it. A good quaner. Using Page 2, we load RegisterB with way of producing harmonically-rich All that remainsis to inserlloop points PAN.VC,which can be sbenin Figure11. waveformsis to use Page5 and createa on Page 7 or Page 4, and adjust the The breath chiff is clearlyvisible at the few segmentsspread across those un- attackand damping on Page7. I beginning of the sound, but unfortu- used by the chiff. Figure12 gives the nately,the sampling staded a fractiontoo general idea - note that the created soon, and the waveform has a few initial waveforms are all ditferent. So what segmentsof low-levelrubbish - nothing about the segmentsin between?Well, to do with Electronic Soundmaker, you this is whereMERGE comes in handy, understand. The cure is to rotate the fillingin the ZEROed segments,and voice left to bring the start of the sound usingthe segmentscreated on Page5 as proper coincident with the start of the the start and end points. RAM. OK, so far it sounds quite interesting The next step is to flick to Voice 1 in timbrally(and looks it too, as Figure13 RegisterA and ZERO it. Usinga new shows) but it's still in need of some command, TRANSFER, the first few amplitude variation. An easy way to segmentsfrom PAN.VCcan be copiedto achieve this is to invert a couple of the blank voice currentlyselected. Stab- segments(numbers 32 and 96, say)and bing the keyboardat this luncturereveals l.lI X from segments1 to 32, 64 to 32, 64 thatall is well,so the nextthing to do is to to 96 and 128 to 96, using Page6. lf you \ t've tusr aou6l{T THts NErrrr IT CONTAINS ALLOF THE TECHNIQUES ilow I CANCOI PoSE LIK! A{oZABT 'meon-Ruro-col PoSER'- SoFTWARE ANO STYLES OF IHEWONLDs GREAT. AltD BEEtHoylr frL Dl lll6^-f^/{out ONLY COST T5OOI EST COMPOSERS!.?ANTUi}| THE IN NO TI'',IE! lETs SEEWKAT THE 'I\E /l osr BoRDtGAxD,r{tDtocRrsolt6. PRO6RAM DOESWITH TITATPIECE Er r ADLt c nstp oF nAtBlENT rraUSlCt DtD IAST rltoHT.t ,flo.l$""r!L.os1 i+/.€oD