Musical Applications of Microprocessors (The Hayden microcomputer series)

835 Pages·1980·42.492 MB·English

by  Hal Chamberlin

MusicalApplications of
Microprocessors

MusicalApplications of
Microprocessors
SECONDEDITION
HalChamberlin
HAYDEN BOOKS
ADivisionofHoward~Sams&Company
4300West62ndStreet
Indianapolis,Indiana46268USA
© 19B5 by Hayden Books
A Division ofHowardW. Sams& Co.
SECOND EDITION
SECOND PRINTING-19B7
Allrights reserved. Nopart ofthis book shall be reproduced, storedina
retrievalsystem, or transmitted by anymeans, electronic, mechanical,
photocopying, recording, or otherwise, without writtenpermission from the
publisher. No patent liabilityis assumedwithrespect to theuseof the
informationcontained herein. Whileeveryprecautionhas been takenin
thepreparationofthis book, thepublisherassumes noresponsibilityfor
errors or omissions. Neither is any liability assumed for damages resulting
from theuse oftheinformationcontained herein.
InternationalStandardBook Number: 0-8104-5768-7
Library ofCongress CatalogCardNumber: 85-24842
Acquisitions Editor: Therese A. Zak
Editors:Ronnie GroffandLori Williams
Illustrator:John McAusland
CoverDesign:Jim Bernard
Printedin the United States ofAmerica
Preface
The period encompassing the mid-1970s until now has seen an explosive
growth in the application ofdigital logic, especially programmed logic and
microcomputers. The key to this growth is the fantastic reduction in the cost
of logic and memory and the development of the microprocessor. In
particular, microprocessors and microcomputer systems built around them
make it possible, practical, and even advisable to perform many functions
using computer techniques that would have been done with conventional
logic or analog circuits a very few years ago.
Although many computer music techniques were developed over a
decade earlier, their widespread use in the broader area of electronic music
has not yet materialized. Now, however, the increasing power of mi
croprocessors and their fantastic low cost make such widespread use inevita
ble.
Many of'these existing techniques cannot or should not be used di
rectly, however. Although a microprocessor bears considerable resemblance
to the large-scale machines on which these techniques were developed, there
are important differences. Additionally, there are numerous new techniques
that lend themselves well to microprocessor implementation but that are
completely impractical using alarge-scale mainframe or even minicomputer.
In the pages to follow, the application ofall important electronic and
computer music performance techniques to microprocessors will be covered.
In addition, some new, not generally known, techniques that are only
practical with microprocessors will be discussed. Finally, some of the
extremely powerful big computer signal-processing techniques will be
presented in nonmathematical language and applied to the more powerful
16-bit microprocessors that are becoming commonplace.
The text is divided into four major sections. Chapters 1 to 5 cover
important background material, the understanding ofwhich is necessary for
full appreciationofthesections tofollow. Chaptersonanalogmusic synthesis
principles, digital music synthesis principles, and microprocessors should
serve to acquaint the general reader with these areas as well as fill in the
background of the specialized reader.
Chapters 6 to 11 covertheapplication ofmicroprocessors tocontrolling
conventional analog sound-synthesizing equipment. The firse two chapters
cover typical analog modules and interfacing techniques to microprocessors.
The remaining four chapters are devoted to the control function itself, par
ticularly the manner in which the human user interacts with the
microprocessor-.synthesizer combination.
Chapters 12 to 18 concentrate on purely digital synthesis techniques.
These techniques have the greatest inherent general.ity and accuracy, but
widespread usehas so far been inhibited by high costand operationoutsideof
real time. Chapter 12 discusses the conversion ofhigh-fidelity audio signals
to and from the digital domain. Chapters 13 to 15 discuss digital signal
generation and processing. The next three chapters describe the use and
implementation of these digital techniques into practical equipment and
systems.
SectionIV covers actual applications ofall ofthese techniques. Chapter
19 describes professional-quality usage of analog and digital technology in
research installations and in several representative products. Chapter 20
examines the design ofconsumer-oriented and verylow-costmusic-synthesiz
ing products. In so doing, it also provides a good summary ofthe strengths
and weaknesses of the myriad synthesis techniques described in earlier
chapters. Chapter 21 concludes by speculating on future developments in
musical applications ofmicroprocessors at all levels from novelties to serious
musical research.
Throughout the discussions, the use ofmathematics is minimized, and
where present, is limited to elementary algebra and trigonometry. Instead,
numerous charts, graphs, and sometimes computer programs in BASIC are
used to illustrate important concepts. This does not mean that the more
difficult conceptsare skipped. Forexample, thefast Fourier transform and its
workings are described and supported with a tested program listing in
BASIC. Digital filters are also covered extensively.
The reader is notexpected to merely studyand marvel at the techniques
described. Rather, he isurged togooutand try them, apply them, and enjoy
the results. For this purpose, many actual programs and circuit diagrams are
included. Whilenotevery topic isreduced topractice, enough information is
supplied orpointed out in reference material to enable the industrious reader
to experiment with and refine the technique.
HALCHAMBERLIN
Contents
SECTION 1. Background 1
1. Music Synthesis Principles 3
Goals ofMusic Synthesis 4
The FundamentalParameters ofSound 8
History ofElectronic SoundSynthesis 34
2. Sound Modification Methods 43
Sound on Tape 43
ElectronicSoundModtjication 48
Analysis-SynthesisMethods 70
3. Voltage Control Methods 75
TypicalModuleCharacteristics 76
Signal Levels in the Synthesizer 81
Some TypicalModules 84
Other~oduus 92
A Typical Patch 94
4. Direct Computer Synthesis Methods 101
Limitations ofVoltage Control 101
Sound in Digital Form 106
A TypicalDirectComputerSynthesis Installation 113
ComputationofSoundWaveforms 116
MusicProgrammingSystemsandLanguages 121
5. Microprocessors 125
MicroprocessorTerminology 126
BriefHistory ofMicroprocessors 127
MicrocomputerPertpheralDevices 139
MicrocomputerSoftware 148
ExampleMicroprocessorDescrtptions 151