ELECTRONICS, MUSIC AND COMPUTERS by Alan Conway Ashton December 1971 UTEC-CSc-71-117 ACKNOWLEDGEMENTS I wish to thank Professor Robert S. Barton for his motivation, stimulation and ideas in special-purpose systems design, information., representation and programming structures. I appreciate the patience and encouragement of Professors David C. Evans and William J. Viavant during my graduate study. I am particularly indebted to Robert Bennion for many design suggestions, interesting discussions and the hardware implementation of the prototype equipment. INTRODUCTION Electronic and Computer Technology has had and will continue to have a marked effect in the field of music. Through the years scien­ tists, engineers, and musicians have applied available technology to new musical instruments, innovative musical sound production, sound analysis, and musicology. At the University of Utah we have designed and are implementing a communication network involving an electronic organ and a small computer to provide a tool to be used in music per­ formance, the learning of music theory, the investigation of music notation, the composition of music, the perception of music, and the printing of music. The computer-aided music tool is shown in figure 1. The computer serves as a communications device that aids the user by performing several functions such as the storage of information, performance of pre-assigned sequences, and retrieving of specific stored data. The computer receives input from a typewriter keyboard, a light pen attach­ ed to the display scope, the organ manuals, pedals, and stop settings. In turn, the computer controls the audio tone production, lights which indicate the organ keys, the display scope and a color generator. There are many interesting things which can be done with this hybrid configuration; for instance, computer assisted learning of music can be investigated, experiments of sensory perception may be carried out, keyboard performance can be studied and new sounds, rhythms and melodies may be intricately interwoven. I will discuss these and other possibilities further after I describe the computer-aided music tool 2 fully (chapter 4). But first, it will be instructive to look at some acoustic properties of sound, the development of electronic musical instruments and the use of computers in the field of music so that in the overall picture the value and position of our system can be assessed and evaluated. Finally, I will look at recent trends and speculate on the future of electronics and computers in the field of music. ■ „ TABLE OF CONTENTS Page ACKNOWLEDGEMENTS .............................................. ' ii A B S T R A C T ................................................. .. v INTRODUCTION ................................................... 1 CHAPTER 1 MUSIC ENGINEERING ................................ 4 Waveform Generation ..................................... 5 Waveform Modification ................................... 12 Sound Coordination and Organization......... .. 25 Waveform Storage.......................................... 30 Sound Control............................................ 32 Music Notation............................................ 40 CHAPTER 2 HISTORICAL DEVELOPMENT OF ELECTRONIC MUSICAL INSTRUMENTS ....................................... 43 Novel Experiments before the Vacuum T u b e ............ 43 Early Developments before World War I.............. I 45 Extentions of the Early Developments................... 63 Electronically Controlled Synthesizers................ 76 CHAPTER 3 COMPUTERS AND MUSIC .............................. 89 Generation of Sound Waveforms......................... 89 Music Composition....................................... 92 Music Printing............................................ 95 Music A n a l y s i s .......................................... 96 Musicology................................................. 100 E d u c a t i o n ................................................ 101 Control of Music-Generating Media..................... 102 iii CHAPTER 4 THE COMPUTER AIDED MUSIC T O O L .....................105 General Description......... ........................... .. 105 The Organ Interface ..................................... .. 108 Internal Representation . .............................. .. 116 Data File Structure..................................... .. 129 E x a m p l e s....................................... .......... 144 Extensions................................................... 147 CHAPTER 5 USES, CAPABILITY AND EVALUATION OF THE MUSICATIONAL T O O L ................................... 150 Music Performance......................... ............. .. 152 Education .................................................... 156 C o m p o s i t i o n ................................................. 160 Score Writing ............................................ .. 161 Study of Multisensory Perception 163 R E F E R E N C E S ........................................................ 167 iv ABSTRACT* The uses of electronic and computer technology in music are . surveyed and a computer-aided music tool is described which consists of a small computer, electronic organ, and a line-drawing display ' scope. The computer receives input from a teletypewriter keyboard, the organ keys and stop tablets. The input information is processed according to stored programs, and output is directed to the organ tone generators, filter selection switches, lights which designate the manual keys, volume control and the display scope. Thus, the organ is full-duplexed through the computer, since the keys are not directly .connected to the tone generators, but are linked via the computer. A basic internal representation of stored music is developed which consists of an interpreted file containing a sequence of variable length commands and typed data. Information transfer rates of a secondary storage tape cassette recorder is adequate for most classi­ cal organ selections, which may be directly entered into the computer by performance on the manual keyboards and pedals, or keyed-in, note by note, either from another type keyboard or from the organ keys themselves. The interactive organ-computer communication network allows real time visual, aural and written response. This makes the musicational ★ i i . This report reproduces a thesis of the same title submitted to the Department of Electrical Engineering, Division of Computer Science, University of Utah, in partial fulfillment of the requirements for the degree of Doctor of Philosophy. v tool, as it is called, useful for programmed music courses, computer aided instruction of music theory, harmony and keyboard performance, ‘ and conducting human information processing experiments in the inves­ tigation of multisensory perception. _ The methods of music production, processing power, and capabilities of the musicational tool are compared to the techniques of other elec­ tronic. and computer-aided musical instruments and the influence of . electronic and computer technology in music of the future is discussed. 3 Lights which illuminate the music keys Figure 1 The Musicational Tool CHAPTER 1 MUSIC ENGINEERING The auditory sensation sound is produced by the impact on the eardrum of a pressure wave propagated in an elastic medium.. Thus, sound results when air or some other medium is set into motion. The frequency of a sound wave is the number of recurrent waves passing a certain observation point per second. The physiological sensation depending mostly on frequency is pitch. Auditory perception of the intensity or energy contained in a sound wave is the loudness of sound In other terms, the volume of sound is the physiological counterpart to the amplitude of the wave. * Sounds may be organized into five main categories [71]. 1) "Pure" tones, 2) ordinary musical tones, 3) clangorous sounds, 4) ordinary noises, and ~ 5) white noise. The first category consists of pure sine waves which can be re­ presented as a function of time as s (t) = Asin(2irft + y) where A is the amplitude, f the frequency and y the phase shift of the sine wave. The sound of a sine wave to a listener is dull and becomes tiresome after a while due to the exact repetition of the waveform. The second group of sounds in their steady state condition may be represented as 00 a mixture of sine tones represented by a Fourier Series: S(t)Z = ' n=l A sin(27rnft + y ). Two interesting waveforms in this group are square n n waves and sawtooth waves. A square wave contains only odd harmonics oo A 1 and can be represented as S(t) = Z — sin [ (2n-l) 2irft]. The result , 2n-l n=l of a square wave is a hollow sound, much like that of a clarinet. A sawtooth wave contains harmonics whose amplitudes are inversely pro- “ n Al portional to their frequencies and is represented as S(t) = Z — sin2mrft. n=ln n A sawtooth wave produces a buzzing-like sound not very dissimilar from that of an English Horn. The third category of sounds consists of those having inharmonic partials and include sounds produced from bells, gongs and cymbals. The next group.is.comprised of any kinds of sounds occur- ing contiguously, and the final category is composed of sizzling, hissing and howling noises in which"a±i audible frequencies occur at random times. Music is the auditory perception of sounds which have been organ­ ized in some meaningful way. Electronic music is that music which is produced, modified or combined with the aid of electronic equipment. The organizational procedure of electronic music