Music Technology Series Acoustics and Psychoacoustics, 2nd edition (with web site) David M. Howard and James Angus Composing Music with Computers (with CD-ROM) Eduardo Reck Miranda Computer Sound Design: Synthesis Techniques and Programming, 2nd edition (with CD-ROM) Eduardo Reck Miranda Desktop Audio Technology Francis Rumsey Digital Sound Processing for Music and Multimedia (with web site) Ross Kirk and Andy Hunt Network Technology for Digital Audio Andrew Bailey Sound and Recording: An introduction, 4th edition Francis Rumsey and Tim McCormick Sound Synthesis and Sampling, 2nd edition Martin Russ Spatial Audio Francis Rumsey
Sound Synthesis and Sampling Second Edition
Martin Russ
AMSTERDAM BOSTON HEIDELBERG LONDON NEW YORK OXFORD PARIS SAN DIEGO SAN FRANCISCO SINGAPORE SYDNEY TOKYO Focal Press is an imprint of Elsevier
Focal Press 200 Wheeler Road, Burlington, MA 01803 First published 1996 Reprinted 1998,1999,2000 (twice), 2002 (twice) Second edition 2004 Copyright © 1996,2004, Martin Russ, All rights reserved. The right of Martin Russ to be identified as the author of this work has been asserted in accordance with the Copyright, Designs and Patents Act 1988 No part of this publication may be reproduced in any material form (including photocopying or storing in any medium by electronic means and whether or not transiently or incidentally to some other use of this publication) without the written permission of the copyright holder except in accordance with the provisions of the Copyright, Designs and Patents Act 1988 or under the terms of a licence issued by the Copyright Licensing Agency Ltd, 90 Tottenham Court Road, London, England WIT 4LP. Applications for the copyright holder's written permission to reproduce any part of this publication should be addressed to the publisher Permissions may be sought directly from Elsevier's Science & Technology Rights Department in Oxford, UK: phone: (+44) 1865 843830, fax: (+44) 1865 853333, e-mail:
[email protected]. You may also complete your request on-line via the Elsevier homopage (http://www.elsevier.com), by selecting 'Customer Support' and then 'Obtaining Permissions' British Library Cataloguing in Publication Data Russ, Martin Sound synthesis and sampling. - 2nd ed. - (Music technology series) 1. Computer sound processing 2. Synthesizer (Musical instrument) I. Title 786.7'4 Library of Congress Cataloguing in Publication Data A catalogue record for this book is available from the Library of Congress. ISBN 0 240516923 For information on all Focal Press publications visit our website at http://books.elsevier.com Typeset by Charon Tec Pvt. Ltd, Chennai, India Printed and bound in Meppel, The Netherlands by Krips bv.
Contents Series introduction Preface to first edition Preface to second edition Visual map About this book
ix x xi xii xiii
BACK ROUND 1 pound B 1.1 ki What is synthesis? 1.2 Beginnings 1.3 Telecoms research 1.4 Tape techniques 1.5 Experimental versus popular musical uses of synthesis 1.6 Electro-acoustic music 1.7 From academic research to commercial production... 1.8 Synthesised classics 1.9 Synthesis in context 1.10 Electronics and acoustics: fundamental principles 1.11 Digital and sampling 1.12 MIDI (Musical instrument digital interface) 1.13 After MIDI 1.14 Questions Timeline
1 3 3 11 13 16
TECHNIQUES
69
2 Analogue synthesis 2.1 Analogue and digital 2.2 Subtractive synthesis 2.3 Additive synthesis 2.4 Other methods of analogue synthesis 2.5 Topology 2.6 Early versus modern implementations 2.7 Example instruments 2.8 Questions Timeline
21 22 23 27 29 32 46 55 58 59 60
71 71 75 109 120 129 137 145 149 150
3
Hybrid synthesis
Wavecycle Wavetable DCOs (Digital controlled oscillators) S&S (Sample and synthesis) Early versus modern implementations Example instruments Questions Timeline 4 Sampling
155
3.1 3.2 3.3 3.4 3.5 3.6 3.7
156 165 172 181 191 193 196 196 197
4.1 4.2 4.3 4.4 4.5 4.6
198 201 203 215 216 218 219 223
Tape-based Analogue sampling Digital Convergence of sampling with S&S synthesis Example equipment Questions Timeline 5 Digit al synthesis 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9
FM Waveshaping Modelling Granular synthesis FOF and other techniques Analysis-synthesis Hybrid techniques Example instruments Questions Timeline
224 241 246 257 259 267 274 275 280 281
APPLICATIONS
285
6 Using synthesis
287
6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 6.9
Arranging Stacking Layering Hocketing Multi-timbrality and polyphony GM On-board effects Editing Questions Timeline 7 Controllers 7.1 7.2 7.3 7.4 7.5 7.6 7.7
Controller and expander MIDI control Keyboards Keyboard control Wheels and other hand-operated controls Foot controls Ribbon controllers
287 289 292 294 296 304 307 317 327 328 330 331 333 339 342 342 344 346
Contents
7.8 7.9 7.10 7.11 7.12
Wind controllers Guitar controllers Advantages and disadvantages Front panel controls Questions
Performance 8.1 Synthesis live 8.2 The role of electronics 8.3 Drum machines 8.4 Sequencers 8.5 Workstations 8.6 Accompaniment 8.7 Groove boxes 8.8 Dance, clubs and DJs 8.9 Studios on computers 8.10 Performance unravelled 8.11 Questions ANALYSIS
347 348 349 350 353 Time line 353 355 355 362 363 371
383
387 Timeline 387 391
9 The future of synthesis 9.1 Closing the circle 9.2 Control 9.3 Commercial imperatives
393 393 394 396
References
399
Glossary
403
Jargon
436
Index
444
Series introduction The Focal Press Music Technology Series is intended to fill a growing need for authoritative books to support college and university courses in music technology, sound recording, multimedia and their related fields. The books will also be of value to professionals already working in these areas and who want either to update their knowledge or to familiarise themselves with topics that have not been part of their mainstream occupations. Information technology and digital systems are now widely used in the production of sound and in the composition of music for a wide range of end users. Those working in these fields need to understand the principles of sound, musical acoustics, sound synthesis, digital audio, video and computer systems. This is a tall order, but people with this breadth of knowledge are increasingly sought after by employers. The series will explain the technology and techniques in a manner which is both readable and factually concise, avoiding the chattiness, informality and technical woolliness of many books on music technology. The authors are all experts in their fields and many come from teaching and research backgrounds. Dr Francis Rumsey Series Consultant
Preface to first edition This is a book about sound synthesis and sampling. It is intended to provide a reference guide to the many techniques and approaches that are used in both commercial and research sound synthesizers. The coverage is more concerned with the underlying principles, so this is not a 'build your own synthesizer' type of book, nor is it a guide to producing specific synthesised sounds. Instead it aims to provide a solid source of information on the diverse and complex field of sound synthesis. As well as the details of the techniques of synthesis, some practical applications are described to show how synthesis can be used to make sounds. It is designed to meet the requirements of a wide range of readers, from enthusiasts to undergraduate level students. Wherever possible, a nonmathematical approach has been taken, and the book is intended to be accessible to readers without a strong scientific background. This book brings together information from a wealth of material which I have been collecting and compiling for many years. Since the early 1970s I have been involved in the design, construction and use of synthesizers. More recently this has included the reviewing of electronic musical instruments for Sound on Sound, the leading hi-tech music recording magazine in the UK. The initial prompting for this book came from Francis Rumsey of the University of Surrey's Music Department, with support from Margaret Riley at Focal Press. I would like to thank them for their enthusiasm, time and encouragement throughout the project. I would also like to thank my wife and children for putting up with my disappearance for long periods over the last year. Martin Russ February 1996
Preface to second edition This second edition has revised and updated all of the material in the first edition, correcting a few minor errors, and adding a completely new chapter on performance aspects (Chapter 8), which shows how synthesizers have become embedded within more sophisticated musical performance instruments, rather than always being standalone synthesizers per se. This theme is also explored further in the extended 'Future of synthesis' chapter. I have strived to maintain the abstraction of the techniques away from specific manufacturers, and with only a few exceptions, the only place where details of individual instruments or software will be found is in the 'Examples' sections at the end of each chapter. Taking a cue from other books in the Focal Press Music Technology series, I have added additional notes alongside the main text, which are intended to reinforce significant points. I must thank Beth Howard and others at Focal Press who have helped me to finish this edition. Their patience and support has been invaluable. I would also like to thank the many readers, reviewers and other sources of feedback for their suggestions, as many as possible of these have been incorporated in this edition. I welcome additional suggestions for improvement, as well as corrections: please send these to me via Focal Press. Martin Russ October 2003
Visual map Background
1 Background
1.1-1.9 Context 1.10 Electronics and acoustics 1.11 Digital and sampling 1.12 MIDI
Techniques Techniques
2 Analogue synthesis
2.2 Subtracts 2.3 Additive
3 Hybrid synthesis
3.1-3.2 Waves 3.4 Sample and synthesis
4 Sampling
4.2 Analogue 4.3 Digital
5 Digital synthesis
5.1 FM 5.2 Waveshaping 5.3-5.4 Modelling 5.6 Analysis-synthesis
Applications
6 Using synthesis
6.1-6.4 Arranging 6.5-6.7 Timbres 6.8 Editing
7 Controllers 8 Performance
Analysis
9 The future of synthesis
Reference
References Glossary Jargon Index
8.3 Drums 8.4 Sequencers 8.5 Workstations
About this book This book to divided into nine chapters, followed by References, Glossary, Jargon and finally, an Index. The Jargon section is designed to try and prevent the confusion that often results from the wide variation in the terminology which to used in the field of synthesizers. Each entry consists of the term which to used in this book, followed by the alternative names which can be used for that term.
Book guide The chapters can be divided into five major divisions: • • •
Background Techniques Applications
•
Analysis
•
Reference
Background
Chapter 1 sets the background, and places synthesis in a historical perspective. Techniques
Chapters 2-5 describe the main methods of producing and manipulating sound. Applications
Chapters 6-8 show how the techniques described can be used to synthesise sound and music, in the studio and in live performance. Analysis
Chapter 9 provides analysis of the development of sound synthesis and some speculation on future developments. Reference References, Glossary, Jargon and Index.
About this book
Chapter guide Chapter 1 Background This chapter introduces the concept of synthesis, and briefly describes j the history. It includes brief overviews of acoustics, electronics, digital sampling and musical instrument digital interface (MIDI).
Chapter 2 Analogue synthesis This chapter describes the main methods which are used for analogue sound synthesis: subtractive, additive, AM, FM, ring modulation, ringing oscillators and others.
Chapter 3 Hybrid synthesis This chapter shows the way that synthesis techniques changed from the primarily analogue electronic circuit designs of the 1960s and 1970s, to the predominantly digital circuitry of the 1980s and 1990s. Synthesizers whose design incorporates a mixture of both design techniques are included.
Chapter 4 Sampling This chapter describes the three types of sampling technology: tape, analogue and digital. It also looks at the continuing convergence between sampling and synthesis by looking at sampling and synthesis (S&S) synthesizers.
Chapter 5 Digital synthesis This chapter looks at the major techniques which are used for digital sound synthesis: FM, waveshaping, physical modelling, granular, FOF, analysis-synthesis and resynthesis.
Chapter 6 Using synthesis This chapter deals with the use of synthesis to make music and other sounds.
Chapter 7 Controllers This chapter looks in detail at how synthesizers are controlled, including using MIDI.
Chapter 8 Performance This chapter looks at the ways that synthesizers can be used in live performance.
Chapter 9 The future of synthesis This chapter attempts to place sound synthesis in a wider context, by describing the probable development of music, MIDI and computing in the future.
About this book
Chapter section guide Within each chapter, there are sections which deal with specific topics. The format and intention of some of these may be unfamiliar to the reader, and thus they deserve special mention. Examples These sections are illustrated with block diagrams of the internal func tion and front panel controls of some representative example instru ments or software, together with some notes on their main features. This should provide a more useful idea of their operation than just black and white photographs. Further information and photographs of a wide range of synthesizers and other electronic musical instru ments can be found in Julian Colbeck's comprehensive Keyfax books (Colbeck, 1985). Details on some specific instruments can be found in Mark Vail's Vintage Synthesizers (Vail, 1993) book, which is a collection of articles from the American magazine Keyboard. Time line The Time lines are intended to show the development of a topic in a historical context. Reading text which contains lots of references to dates and people can be confusing. By presenting the major events in time order, the developments and relationships can be seen more clearly. The time lines are deliberately split up so that only entries relevant to each chapter are shown. This keeps the material in each individual time line succinct. Overall time line Chapters 2-5 of this book do not represent a linear historical record, even though the apparent progression from analogue, via hybrid, to digital synthesis methods is a compelling metaphor. Synthesis techniques, like fashion, regularly recycle the old and mostly forgotten with 'retro' revivals of buzzwords like FM, analogue, valves, FETs, modular, resynthesis and more. The overall timeline shown overleaf is intended to show just some of the complex flow of the synthesis timeline. Questions Each chapter ends with a few questions, which can be used as either a quick comprehension test, or as a guide to the major topics covered in that chapter.
About this book
Metronome patented
1815
First magnetic tape recorder First true commercial magnetic tape recorder
Performance 1920
1937
RCA mark II synthesizer
Sampling Sampling
1955
Analogue
Buchla black box, early analogue synth
1963
Analogue
Mellotron Wendy Carlos's 'switched on bach' Mini Moog launched
1965 1968 1969
Sampling Performance Analogue
Ralph Deutsch electronic piano
1970
Hybrid
Roland TR-33 Rhythm Unit Roland MC-4 Sequencer Fairlight CMI Fairlight CMI
1972 1978 1979 1979
Performance Digital Hybrid Sampling
Wasp synthesizer uses hybrid of analogue and digital
1980
Digital
First dedicated sampler: emulator CD launched PPG 2.2 polyphonic hybrid synth Yamaha DX7 first commercial all-digital synth TR-909 First MIDI drum machine Roland MC-202 Micro-composer Ensoniq mirage: affordable sampler Roland D50 digital synth Waldorf Microwave wavetable synth
1980 1982 1982 1983 1983 1984 1984 1987 1989
Sampling Digital Hybrid Digital Performance Performance Sampling Digital Hybrid
Roland JD-800 analogue polysynth
1991
Analogue
Roland DJ-70 sampling workstation Yamaha VL1 physical modelling synth Digidesign ProTools free Roland MC-303 Groovebox Yamaha AN 1X analogue modelling synth Yamaha DJ-X mass-market sampling groovebox
1992 1994 1995 1996 1997 1998
Performance Digital Sampling Performance Digital Performance
Reason virtual studio in a rack software
2001
Digital
Yamaha RS7000 Music Production Studio Hard disk recorder, mixer and CD-writer in one box
2001 2001
Performance Digital
Time
Background
1 Background This chapter introduces the concept of synthesis, and briefly describes the history. It includes brief overviews of acoustics, electronics, digital sampling and musical instrument digital interface (MIDI).
1.1
What is synthesis?
'Synthesis' is defined in the 2003 edition of the Chambers 21stCentury Dictionary as -building up; putting together; making a whole out or parts'. The process of synthesis is thus a bringing together, and the 'making a whole' is significant because it implies more than just a random assembly: synthesis should be a creative process. It is this artistic aspect, which is often overlooked in favour of the more technical aspects of the subject. Although a synthesizer may be capable of producing almost infinite varieties of output, controlling and choosing them requires human intervention and skill. The word 'synthesis' is frequently used in just two major contexts: the creation of chemical compounds and the production of electronic sounds. But there are a large number of other types of synthesis. 1.1.1
Types
All synthesizers are very similar in their concept - the major differences are in their output formats and the way that they produce that output. Just some of the types of synthesizers are as follows: • • • • • •
Texture synthesizers, used in the graphics industry, especially in 3D graphics. Video synthesizers, used to produce and process video signals. Colour synthesizers, used as part of 'son et lumiere' presentations. Speech synthesizers, used in computer and telecommunications applications. Sound synthesizers, used to create and process sounds and music. Word synthesizers, more commonly known as authors using 'word processor' software!
Synthesizers have two basic functional blocks: a control interface, which is how the parameters which define the end product are set; and a 'synthesis engine', which interprets the parameter values and produces the output. In most cases there is a degree of abstraction involved between the control interface and the synthesis engine itself. This is because the complexity of the synthesis process is often very high, and it is often necessary to reduce the apparent complexity of the control by using some sort of simpler conceptual model This enables the user of the synthesizer to use it without requiring a detailed knowledge of the inner workings. This idea of models and abstraction of interface is a recurring theme which will be explored many times in this book (Figure 1.1.1). 3
Figure 1.1.1 The user uses a metaphor in order to access the functions of the synthesizer. The synthesizer provides a model to the user and maps this model to internal functionality. This type of abstraction is used in a wide variety of electronic devices, particularly those employing digital circuitry.
Many members of the general public have unrealistic expectations of the capabilities of synthesizers. The author has encountered feedback comments such as 'I thought it did it all by itself!' when he has shown that he can indeed 'play* a synthesizer.
Although synthesizer can be spelt with a 'zer' or 'ser' ending, the 'zer' ending will be used in this book. Also, the single word 'synthesizer' is used here to imply 'sound synthesizer, rather than a generic synthesizer.
Note that the production of a wide range of sounds by a synthesizer can be very significant. A 'synthesizer' which produces a restricted range of sounds can often be viewed as being more musically acceptable.
1.1.2 Sound synthesis Sound synthesis is the process of producing sound. It can reuse existing sounds by processing them, or it can generate sound electronically or mechanically. It may use mathematics, physics or even biology; and it brings together art and science in a mix of musical skill and technical expertise. Used carefully, it can produce emotional performances, which paint sonic landscapes with a rich and huge set of timbres, limited only by the imagination and knowledge of the creator. Sounds can be simple or complex, and the methods used to create them are diverse. Sound synthesis is not solely concerned with sophisticated computer-generated timbres, although this is often the most publicised aspect. The wide availability of high quality record ing and synthesis technology has made the generation of sounds much easier for musicians and technicians, and future developments promise even easier access to ever more powerful techniques. But the technology is nothing more than a set of tools which can be used to make sounds: the creative skills of the performer, musician or techni cian are still essential to avoid music becoming mundane. 1.1.3 Synthesizers Sounds are synthesised using a sound synthesizer. The synthesis of sounds has a long history. The first synthesizer might have been an early ancestor of Homo sapiens hitting a hollow log, or perhaps learn ing to whistle. Singing uses a sophisticated synthesizer whose cap abilities are often forgotten: the human vocal tract. All musical instruments can be thought of as being 'synthesizers', although few people would think of them in this context. A violin or clarinet is viewed as being 'natural', whereas a synthesizer is seen as 'artificial', even though all of these instruments produce a sound by essentially synthetic methods. Recently, the word 'synthesizer' has come to only mean an electronic instrument that is capable of producing a wide range of different sounds. The actual categories of sounds which qualify for this label of synthesizer are also very specific: purely imitative sounds are frequently regarded as nothing other than recordings of the actual instrument, in which case the synthesizer is seen as little more than a replay device. In other words, the general public seems to expect synthesizers
The electronic piano is one example, where the same synthesis capability could be packaged in two different ways, and would consequently be sold separately to synthesists and piano players.
to produce 'synthetic' sounds. This can be readily seen in many lowcost keyboard instruments which are intended for home usage: they typically have a number of familiar instrument sounds with names like 'piano', 'strings', 'guitar', etc. But they also have sounds labelled 'synth' for sounds which do not fit into the 'naturalistic' description scheme. As synthesizers become better at fusing elements of real and synthetic sounds, the boundaries of what is regarded as 'synthetic' and what is 'real' are becoming increasingly diffuse. This blurred perception has resulted in broad acceptance of a number of 'hyper-real' instrument sounds, where the distinctive characteristics of an instrument are exaggerated. Fret buzz and finger noise on an acoustic guitar and breath noise on a flute are just two examples. Drum sounds are frequently enhanced and altered considerably, and yet, unless they cross that boundary line between 'real' and 'synthetic', their generation is not questioned - it is assumed to be 'real' and 'natural'. This can cause considerable difficulties for performers who are expected to reproduce the same sound as the compact disk (CD) in a live environment. The actual sound of many live instru- j ments may be very different from the sound that is 'expected' from the familiar recording that was painstakingly created in a studio. Drummers are one example: they may have a physical drum kit where many parts of the kit are present merely to give a visual cue or 'home' to the electronically generated sounds that are being controlled via triggers connected to the drums, and where the true sound of the real drums is an unwanted distraction. Forms Synthesizers come in several different varieties, although many of the constituent parts are common to all of the types. Most synthesizers have one or more audio outputs; one or more control inputs; some sort of display; and buttons or dials to select and control the operation of the unit. The major split is into performance and modular forms: •
•
Performance synthesizers have a standard interconnection of their internal synthesis modules already built-in. It is usually not possible to change this significantly, and so the signal flow always follows a set path through the synthesizer. This enables the rapid patching of commonly used configurations, but does limit the flexibility. Performance synthesizers form the vast majority of commercial synthesizer products. Conversely, modular synthesizers have no fixed interconnections, and the synthesis modules can be connected together in any way. Changes can be made to the connections whilst the synthesizer is making a sound, although the usual practice is to set up and test the interconnections in advance. Because more connections need to be made, modular synthesizers are harder and more time-consuming to set up, but they do have much greater flexibility. Modular synthesizers are much rarer than performance synthesizers, and are often used for academic or research purposes.
Non-ideal interfaces are actually 1 very common. The 'qwerty typewriter keyboard was originally intended to slow down typing speeds and so help prevent the jamming of early mechanical typewriters. It has become dominant (and commercially, virtually essential!) despite many attempts to replace it with more economically efficient alternatives. The music keyboard has also seen several carefully humanengineered improvements which have also failed to gain widespread acceptance. It is also significant that the qwerty and music keyboards have both become metaphors for computers/information and music in general.
Both performance and modular synthesizers can come with or with out a music keyboard. The keyboard has become the most dominant method of controlling the performance aspect of a synthesizer, although it is not necessarily the ideal controller. Synthesizers which do not have a keyboard (or any other type of controller device) are often referred to as expanders or modules, and these can be controlled either by a synthesizer which does have a keyboard or from a variety of other controllers. It has been said that the choice of a keyboard as the controller was probably the biggest setback to the wide acceptance of synthesizers as a musical instrument. Chapter 7 describes some of the alternatives to a keyboard. 1.1.4 Sounds
Synthesised sounds can be split into simple categories like 'imitative' or 'synthetic'. Some sounds will not be easy to place in a definite category, and this is especially true for sounds, which contain elements of both real and synthetic sounds. Imitative sounds often sound like real instruments, and they might be familiar orchestral or band instruments. In addition, imitative sounds may be more literal in nature, the sound effects. In contrast, synthetic sounds will often be unfamiliar to anyone who is used to hearing only real instruments, but over time a number of cliches have been developed: the 'string synth' and 'synth brass' being just two examples. Synthetic sounds can be divided into various types, depending on their purpose. 'Imitations' and 'emulations'
'Imitations' and 'emulations' are intended to provide many of the characteristics of real instruments, but in a sympathetic way where the synthesis is frequently providing additional control or emphasis of significant features of the sound. Sometimes an emulation may be used because of tuning problems, or difficulties in locating a rare instrument. The many 'electronic' piano sounds are one example of an emulated sound. 'Suggestions' and 'hints'
'Suggestions' and 'hints' are sounds where the resulting sound has only a slight connection with any real instrument. The 'synth brass' sound produced by analogue polyphonic synthesizers in the 1970s is an example of a sound where just enough of the characteristics of the real instrument are present and so strongly suggest a 'brass'-type instrument to an uncritical listener, but where detailed comparison immediately highlights the difference to a real brass instrument. 'Alien' and 'off-the-wall'
'Alien' and 'off-the-wall' sounds are usually entirely synthetic in nature. The cues which enable a listener to determine if a sound is
synthetic are complex, but are often related to characteristics that are connected with the physics of real instruments: unusual or unfamiliar harmonic structures and their changes over time; constancy of timbre over a wide range; and pitch change without timbre change. By deliberately moving outside of the physical limitations of convertrional instruments, then it is noise-like. Noise-ike Of course, most synthesizers can also produce variations on 'noise', of which 'white noise' is perhaps the most unpitched and unusual sound of all, since it has the same sound energy in linear frequency bands across the entire audible range. Any frequency-dependent variation of the harmonic content of a noise-like sound can give it a perceivable 'pitch', and it thus becomes playable. All of these types of synthetic sounds can be used to make real sounds more interesting by combining the sounds into a hybrid composite (see Chapter 6). Factory presets Naming sounds is not as straightforward as it might appear at first. For example, if you have more than two or three piano sounds, then manufacturer's names or lots of adjectives tend to be used: Steway piano or 'Detuned pub piano' being simple examples. For sounds which are more synthetic in nature, the adjectives become more dense, or are abandoned altogether in favour of names which suggest the type of sound rather than try and describe it 'crystal spheres' and thudblock' being two examples.
Understanding how a synthesis technique works is essential for tte adjustment (tweaking) of sou wJs to suit a musical J^text and also knowing how
