ALESIS FUSION INTRODUCTION TO SAMPLING The basics..... Sampling is a process where an audio signal is recorded digitally after which it can be played from a musical keyboard and/or triggered from pads, etc.. These recordings (largely known as ‘samples’) form the basis of a sound and can pretty much be regarded as the ‘oscillators’ such as you might find in an analog synthesiser - in fact, many modern products use samples rather than electronic oscillators as the basis for their sounds. Typically, such samples then pass through filters and amplifiers which are controlled by envelopes, LFOs and velocity, etc., much like a standard analog synthesiser. In products that rely on sampled waveforms as the basis of their sounds, this is known as ‘S+S’ or ‘sampling and synthesis’. We will look at the details later in this tutorial. The history..... Musicians and composers have been messing around with recorded sound for many decades. As long ago as the 1940s, composers were recording acoustic sounds and speeding them up and slowing them down and reversing them, looping them and splicing them all together to create collages of manipulated sounds which became known as musique concrete. The grand-daddy of sampling keyboards is not, contrary to popular opinion, the Mellotron but the instrument on which it was based - the Chamberlin. Invented by one Harry Chamberlin in the late 40s, it is said that Chamberlin (a keen home organist and tape recording hobbyist) had the idea that if you could somehow play tape recordings of ‘real’ instruments from some form of musical keyboard, you could play any instrument. Chamberlin managed to make his instrument (in his garage!) and sold quite a few during the ‘50s but being individually hand- built in crude circumstances, reliability was a problem. What happened next, however, is shrouded in myth and mystery. It is said that Chamberlin’s head (and only!) salesman, Bill Fransen, travelled to the UK in search of a reliable supply of tape heads, approaching a Midlands-based company called Bradmatics. Intrigued why someone would want such a large order of tape heads, they met with Fransen and became intrigued by the product concept. What happened during those discussions will probably never been known but a new company was started called ‘Mellotronics’ and the Mellotron went into production. Originally, the Tron was aimed at home organists with pre-recorded drum and accompaniment patterns on one keyboard with melodies and chords played on another. However, in the early ‘60s, the BBC thought this would be ideal for quickly playing sound effects, etc., in radio and TV productions (which, remember, were broadcast live in those days) and several customised Trons were build especially for the Beeb. Then some bright spark had the idea of playing ‘real’ instruments such as strings, flute, choir, etc., and so the Mellotron as we know it was born and was rapidly adopted by many artists and bands in the mid-’60s, appearing on many a hit record. In the ‘70s, the Mellotron became synonymous with prog-rock bands such as Genesis, Yes, King Crimson and others who made the Mellotron a trademark of their sound. With the advance of polyphonic synths, however, the Mellotron soon fell from grace (despite their magnificent sound, they were big and unreliable beasts to have to haul around from gig to gig!). Of course, sampling as we know it came about in 1979 with the release of the seminal Fairlight CMI (Computer Musical Instrument). Originally, however, the Fairlight was intended to be a digital synthesiser and sampling was a kind of bolt-on added bonus. But it was the sampling that captured the imagination of everyone (although you’d have needed a cool $40,000 or more to buy one!!!). Introduction Page 1 ALESIS FUSION INTRODUCTION TO SAMPLING After the Fairlight, the race was on to bring sampling to the masses and the first off the starting block was Emu with their imaginatively titled ‘Emulator’ for a mere (!!) $10,000. This was superseded by the Emulator II which, although more expensive (around $18,000) was much more capable with filters and synth facilities. Arguably one of the biggest advances in promoting ‘affordable’ sampling was the release of the Akai S900 in 1986 which just about offered everything musicians wanted of a sampler (at the time anyway) at a price that people were prepared to pay (around $2,500). Of course, Emu and Akai superseded their products with ever more powerful instruments and other manufacturers entered the arena as well but ultimately, the market was dominated by Akai and Emu. Until, that is, the advent of software samplers. With computers getting more and more powerful with faster CPUs and bigger memory in the ‘90s, it became feasible to create a ‘virtual’ sampler that used the computer’s gubbins instead of dedicated hardware. But therein lies a conundrum - whilst offering very powerful sample playback1 and processing facilities, they lack the dedicated hardware required for efficient playback of samples with often low quality transposition (interpolation), poor and sometimes inaccurate loop playback (because of other strains being placed on the host computer’s CPU that ‘interrupt’ playback), etc.. And whilst it’s all well and good to have samples with high sampling rates and bit-depths that measure in gigabytes rather than megabytes (or kilobytes in the early samplers!), these are taxing on the CPU and reliable performance can often be difficult to achieve (and when a software sampler is hogging almost all of the host computer’s resources, it can be difficult to run other music applications). As such, there is still a place for a hardware sampler even today (despite what many would have us believe). It’s true that the rack-mount format sampler has pretty much disappeared (though tens of thousands - or more - are still in use daily across the world) but this is probably due more to its form factor - rack-mount gear is generally on the decline because it can be so awkward to operate. But to say that the hardware sampler has had its day is incorrect because products such as Akai’s MPC series have never been more popular. And so it is with Fusion, which brings hi-end hardware sampling in a convenient and integrated workstation that is equally at home in the studio or on-stage. With a specification rivalling (if not exceeding!) many of the top hardware samplers ever made, this is not some afterthought or optional extra - it’s an integral part of Fusion to be used alongside the other sound engines with almost unrivalled flexibility. What follows is a ‘generic’ description of sampling in general and is not particularly Fusion- specific (that is described in a separate tutorial). Hopefully, with a fuller understanding of the basic principles of sampling, you can coax more from Fusion’s powerful sampling and sample playback and processing facilities. 1 Very few software samplers actually ‘sample’ - they typically require samples to be recorded externally and then imported somehow. Introduction Page 2 ALESIS FUSION INTRODUCTION TO SAMPLING Voice architecture.... Simplified block diagram of a typical sampler If you have read the analog synthesis tutorial, you will no doubt notice that the diagram shown above looks uncannily similar to a typical analog synthesiser and indeed, they are - the oscillators are simply replaced with samples. After that, the signal flow is almost identical and the samples are processed by filters, envelopes, LFOs. That said, the block labelled ‘sample oscillator’ above is not as simple as it looks. More often than not, there will be several sample oscillators per voice (typically four as on Fusion) and these can be used to layer samples and/or can be used to switch between different samples (typically using velocity) - we shall come to this in due course during this tutorial. For now, thinking of your sampler as a simple analog synth can help simplify things... it’s just that instead of preset waveforms, almost any sound can be used as the sound source! Let’s now have a look at what a sample actually is. Introduction Page 3 ALESIS FUSION SAMPLING TUTORIAL Digitising audio When you record a sample, it is a digital recording. As we know, microprocessors can only deal with noughts and ones. How, then, do we convert continuous analog audio into something that the microprocessor can make sense of? When we record a signal digitally, it is actually sliced up into tiny fragments in an analog to digital converter (ADC): Analog audio input ADC Digital audio output As you can see, the continuous analog audio input is sliced up in the ADC and the output is a ‘stepped’ representation of the incoming signal. Because the waveform is stepped, each of those steps can be given a numeric value that a microprocessor can deal with. Sampling Page 4 ALESIS FUSION SAMPLING TUTORIAL However, because of those steps, the sound is not a truly accurate representation of the original signal. It follows, therefore, that the more slices we take, the more accurate the digital version will be. The number of slices is known as the sample rate. The ‘industry standard’ sample rate today is 44.1kHz - that is, every second of audio is sliced 44,100 times. This gives a fairly accurate representation of the sound and is the standard adopted for CDs giving audio reproduction of up to 20kHz, the upper limits of human hearing. In fact, a good analogy can be made with movies. As we know, movies are actually a series of still photographs which, when played back quickly in succession, gives the illusion of movement.