Download 40791523 Musical Applications of Microprocessors 2ed Chamberlin H 1987 PDF

Title40791523 Musical Applications of Microprocessors 2ed Chamberlin H 1987
TagsDecibel Pitch (Music) Root Mean Square Amplitude Hertz
File Size42.5 MB
Total Pages835
Table of Contents
Section I    Background
	1 Music Synthesis Principles
		Goals of Music Synthesis
			Wider Variety of Sounds
			Performance by the Composer
			Increased Precision
			Increased Complexity
			Increased Spontaneity
		The Fundamental Parameters of Sound
			Typical Sound Waveforms
			The Frequency Parameter
			Musical Pitch
			The Amplitude Parameter
			Frequency and Amplitude Interaction
			The Mathematical Sine Shape
			The Mechanical Sine Shape
			Complex Wavefarms
			Human Ear Interpretation of Waveshape
			Nonrepeating Wavefonns
			Parameter Variation
			Frequency Variation
			Amplitude Variation
			Spectrum Variation
			Simultaneous Sounds
		History of Electronic Sound Synthesis
			The Telehannonium
			Soundtrack Art
			The Tape Recorder
			RCA Mark II Synthesizer
			Direct Computer Synthesis
			Voltage-ControUed Synthesizers
	2 Sound Modification Methods
		Sound on Tape
			Speed Transposition
			Tape Reverberation
			Multitrack Recorders
		Electronic Sound Modification
			Nonlinear Amplifiers
			Vanable Filters
			Spectrum Shifters
			Envelope Modifiers
			Electronic Reverberation
			Chorus Synthesizers
		Analysis-Synthesis Methods
			Envelope Tracking
			Pitch Tracking
			Spectrum Tracking
			Use ofAnalysis Results
	3 Voltage Control Methods
		Typical Module Characteristics
			General Module Types
			A Simple Patch
		Signal Levels in the Synthesizer
			Frequency-Control Relation
			Exponential Relation
			Amplitide Relation
			Standard Voltage Levels
		Some Typical Modules
			Voltage-Controlled Oscillator
			Voltage-Controlled Amplifier
			Voltage-Controlled Filter
			Envelope Generators
			Music Keyboard
		Other Modules
			Sample-and-Hold Module
			White Noise Generator
			Specialized Modifiers
		A Typical Patch
			Frequency Modulation Terminology
			Effect of Deep Frequency Modulation
			Patch for Dynamic Depth FM
	4 Direct Computer Synthesis Methods
		Limitations of Voltage Control
			Simultaneous Sounds
			Direct Computer Synthesis Problems
			Overcoming the Problems
			Proof of Fidelity
			Setting the Sample Rate
			Any Sound Can Be Synthesized
			Signal-to-Noise Ratio
		A Typical Direct ComputerSynthesis Installation
			Minimum System
			Storage of Samples
		Computation of Sound Waveforms
			Sin and Other Built-in Functions
			Fourier Series
			Simultaneous Sounds
			Updating of Parameters
			Table Lookup
			Hardware Aids
			Digital Sound Modification
		Music Programming Systemsand Languages
			Tightly Structured System
			Maximum Flexibility System
			Loosely Structured Systems
	5 Microprocessors
		Microprocessor Terminology
		Brief History of Microprocessors
			The First True Microprocessor
			The First Popular Microprocessor
			The Dawn ofPersonal Computing
			The Altair 8800 Microcomputer
			The First Wave
			The Second Wave
			More Microprocessor Advancements
			Memory Advances
			The Third Wave
		Microcomputer Peripheral Devices
			Main Memory
			Mass Storage
			Floppy Disk
			Winchester Disk
			Text Keyboard
			CRT Display
			Printers and Plotters
			Miscellaneous Devices
		Microcomputer Software
			System Monitor
			Text Editor
			High-Level Language
		Example Microprocessor Descriptions
			The 6502 for Logic Replacement and Low Cost
			Bus Structure and Timing
			Addressing Modes
			Interfacing Tricks
			The 68000 for General Purpose and High Performance
				Bus Structure and Timing
				Addressing Modes
				Instruction Set
Section II   Computer Controlled Analog Synthesis
	6 Basic Analog Modules
		Analog System Standards
			Signal and Control Voltages
			Mechanical Considerations
			Analog Components
		Voltage-Controlled Oscillator
			Fundamental Types
			Exponential Converter
			Compensating Temperature Drift
			Linear Control Input
			Input Processor
			Sawtooth Oscillator
			Practical Schematic
		Voltage-Controned Amplifier
			Controlled Gain Block
			Transconductance Gain Block
			Operational Transconductance Amplifier
			Application of the 3080 OTA
			Exponential Gain Control
			Improving Linearity
			Gilbert Multiplier
			VCA Using the 2020
		Voltage-Controlled Filter
			Variable Gain Tunes a Filter
			Voltage-Tunable Bandpass Filter
			Practical State Variable Filter
			Controlling Q
			Quad Voltage-Controlled Integrator IC
	7 Digital-to-Analog Analog-to-Digital Converters
		Data Conversion Terminology
			Settling Time
		DAC Techniques
			Duty-Cycle Modulation
			Resistor String DAC
			Resistive Divider
			R-2R Ladder
			Segmented DAC
			Exponential DAC Circuits
		Analog Switches for DACs
			Bipolar Transistor Switch
			Junction FET Switch
			MOSFET Switch
			Current-to-Voltage Conversion
		Some Commercial DACs
			1408 and DAC-08 Type for 8 Bits
			Number Coding
			7530 Type for 10 Bits
			Higher-Resolution Units
		Multiplexing DACs
			Analog Multiplexors
			Hold Capacitors
			Channel Output Amplifier
			Refresh Logic
			An Intelligent DAC?
		Analog-to-Digital Converters
			Single-Shot Method
			Dual-Slope Method
			Linear Search and Tracking ADC
			Successive Approximation Search
			Successive Approximation Logic
			Sample and Hold
			Multiplexing ADCs
	8 Signal Routing
		Manually Patched Computer-Controlled System
			Synthesizer Requirements
			Control Computer Requirements
			Computer Inteiface Box
			Automatically PatchedComputer-Controlled System
			Matrix Reduction by Point Elimination
			Reduction by Subgroup Organization
			Reduction Example
			Mechanical Relays
			Semiconductor Analog Switches
		Fixed-Patched Computer-Controlled System
			Voice Module Design
			Increasing Flexibility
			Direct Digital Interface
			Audio Bus
	9 Organ Keyboard Interface
		Adapting a Standard Synthesizer Keyboard for Computer Input
			Gate and Trigger
			Computer Interface
		Polyphonic Keyboards
			Two-Note Keyboard
			Ultimate Limitations
		A Microprocessor-Based Keyboard Interface
			Velocity Sensing
			Keyboard Events
			Hardware Configuration
			Software Functions
			Software Flowchart
			Program Description
	10 Other lnput Methods
		Manual Input Devices
			Ribbon Controller
			Graphic Digitizer
			Modified Musical Instruments
		Algorithmic Input
			Sample-and-Hold Module
			Controlling Randomness
			More Sophisticated Techniques
			Analog Feedback Techniques
			Digital Feedback Techniques
			The Muse
	11 Control Sequence Display and Editing
		Types of Display Devices
			Graphic Display Classifications
			A Simple Vector Display
			Display List Interpreter
			Keeping the Image Refreshed
			Vector Generator Circuit
			Raster Scan Displays
			Display Buffer
			Bit-Mapped Display Interfaces
			Editing the Display List
		Applications of Graphic Displays in Music
			Graphic Input Techniques
			Composition by Editing
			Editing Functions
			Noncontinuous Curves
Section III  Digital Synthesis and Sound Modlification
	12 Digital-to-Analog and Analog-to-Digital Conversion of Audio
		Increasing Dynamic Range
			Brute Force
			Sign-Magnitude Coding
			Segmented DAC
			Floating-Point DACs
			Exponential DACs
			Which Is Best?
		Reducing Distortion
			Low-Glitch DAC Circuits
			Sample-and-Hold Deglitcher
			Slew-Limiting Distortion
			Track-and-Ground Circuit
		Low-Pass Filter
			Low-Pass Filter Model
			Actual Filter Requirements
			Sharp Low-Pass Filter Design
			ltertttive R-C Low-Pass Filter
			BuuenvQrth Response
			Chebyshev Response
			Elliptical Response
			Phase Shift
			Finite Sample Width Compensation
			Building a Chebyshev Filter
			Building an Elliptical Filter
			Digital Anti-Alias Filters
			A Complete Audio DAC
		Audio Digitizing
			A 12-Bit Audio A-to-D Converter
	13 Digital Tone GenerationTechniques
		Direct Waveform Computation
			Digital Sawtooth Oscillator
			Improving Frequency Resolution
			Other Waveforms
			Linear Interpolation
			Alias Distortion
		Table Lookup Method
			Controlling Frequency
			Table Size
			Filling the Table
			Table Filling by Fourier Series
			Dynamic Timbre Variation
			Fourier Transformation
			Characteristics of the Discrete Fourier Transform
			Slow Fourie,. Transform
			Fast Fourier Transform
			Complex Arithmetic
			The FFT Algorithm
			An FFT Subroutine in BASIC
			Modification for Real Data
			Using the FFT for Synthesis
			The Phase-Derivative Spectrum
		Other Digital Tone Generation Techniques
			FM Synthesis
			Which Is Best?
	14 Digital Filtering
		Digital Equivalents of Analog Filters
			Digital R-C Low-Pass Filter
			Signal Flow Graphs
			State-Variable Digital Filter
			Tuning Relationships
			Multiple Feedback Digital Filters
			All-Pass Digital Filter
			Digital Notch Filters
		Filters with an Arbitrary Response
		Reverberation Simulation
			A Practical Filter forConcert Hall Reverberation
		Chorus Effect
			Interpolation Filters
			The Table Method of Interpolation
	15 Percussive Sound Generation
		Types of Percussive Sounds
		Damped Sine Wave Generation
			A "Perfect" Digital Oscillator
		Digital Noise Generation
			Linear Congruential Method
			Shift Register Method
			Using the Random Numbers
			Type 3 Percussive Sounds
		Nonlinear Vibrator Simulation
	16 Source-Signal Analysis
		Spectrum Analysis
			Plotting Methods
			Time-Frequency Resolution
			Data Representation
		Filtering Methods of Spectral Analysis
			A Digital Filterbank Spectrum Analyzer
			Improving the Analyzer
		Spectrum Analysis Using the FFT
			Equivalent Bandpass Filter
			Some Example Windows
			Performing the Analysis
		Spectral Processing
			Direct Spectral Modification
			Parameter Extraction
			Frequency Analysis
			Spectral Shape Anal)'sis
			Linear Prediction
			Homomorphic Analysis
		Pitch Measurement
			Time-Domain Methods
			Frequency-Domain Methods
	17 Digital Hardware
		Analog Module Replacement
			Simple Digital Oscillator Module
			Divide-by-N Frequency Generator
			Rate Multiplier
			Accumulator Divider
			Phase-Locked Loop
			Which is Best?
			Waveshaping the Oscillator Output
			Variable and Constant Sample Rate
		Multiplexed Digital Oscillator
			Hardware Structure
			Inteifacing to the Control Computer
		Fourier Series Tone Generator
			Hardware Structure
			Amplitude Multiplier
			An Intelligent Oscillator?
		Modular Digital Synthesizer
			A Hard-Wired Digital Synthesizer
			Signal-Processing Computer
		Digital Voice-Per-Board System
			A Hybrid Voice Module
	18 Music Synthesis Software
		Organization of Music Software Systems
			Implementation of the Levels
			High-Level Languages
		Low-Level Programming Techniques
			Properties of Binary Arithmetic
			Addition and Subtraction
			Required Arithmetic Instructions
			A Fixed-Point Arithmetic Package for the 6502
			Example Programs
		NOTRAN Music System
			Level 1 Routines
			Level 2 Generator Routines
			Level 2 Sequencing Routine
			NOTRAN Language
			VOICE Statement
			PRCUS Statement
			Control Statements
			Note Statements
			Sequencing and Overlap
			Level 3 Routines
			Level 0 Routines
			Sample Storage Devices
			Playback Program
			The Author's Delayed-Playback Installation
Section IV Product Applications and the Future
	19 Some Real Applications
		Synthesizers in the Real World
			Live Performance Synthesizers
			Studio Synthesizers
			Research Synthesizers
			Music Education
			The Synthesizer Industry
		Hybrid Keyboard Synthesizers
			A Typical Hybrid Synthesizer
			The Rhodes Chroma
			Dual-Channel Voice Board
			Microprocessor Controller
			D-to-A Converter
			External Computer Interface
			Keyboard Scanner
			Control Program and Panel Function
		All-Digital Synthesizers
			Synthesis from Sound Parameters
			Reconstruction of Digital Recordings
			"Toolbox" Synthesizers
		Direct Computer Synthesis Practice
			Real.Time Direct Synthesis
			Delayed Playback Direct Synthesis
	20 Low-Cost SynthesisTechniques
		Applications of Low-Cost Synthesis
		Techniques for Low-Cost Synthesis
			Interface Chip Timers
			Timed Program Loops
			Simplified Direct Synthesis
			Sound Generator ICs
		Low-Cost Synthesis Products
			"Toy" Keyboard Instruments
			Personal Computers
	21 The Future
		The Music Technology Development Cycle
		Major Trends in Electronic Teclmology
			Memory Cost and Capacity
			Microprocessor Power
			Custom Integrated Circuits
			Innovations in Packaging
			Increasing  Knowledge Base
		The Predictions
	Periodicals and Organizations
	A - B
	B - D
	D - F
	F - L
	L - M
	M - P
	P - S
	S - W
Hal Chamberlin web Interview January 30, 2002
Document Text Contents
Page 417


and stopbandattenuationsof 50 to 90 dB are given. Theseshouldcovet the
rangeof applicationfor audio filters from minimum cost experimentalunits
to very sharpprofessionalapplicationunits. The elementvaluesaregiven in
hentiesandfaradsfor a cutoff frequencyof 0.159Hz andimpedancelevel of 1
ohm. To computeactualpracticalcomponentvalues,usethe formulasbelow:

L' = 0.159RL

c' = 0.159C

whereL' and C' are the practical componentvalues,Land C are from the
table, R is the source and termination impedance,and F is the cutoff
frequency. Figure 12-25Cshowsa practical seventhorder parallel resonant
filter designhaving0.28 dB ripple, 60 dB attenuation,a cutofffrequencyof
10 kHz (25 ks/s sample rate), and an impedanceof 5,000 ohms. Figure
12-25Dshowsa fifth orderseriesresonantfilter with 1.25 dB ripple, 40 dB
attenuation,5,180 Hz cutoff (12.5 ks/s samplerate), and lK impedance.

Even considering the advantagesof small size, inexpensivecompo-
nents, etc., of active implementation,actualpassiveimplementationof the
filter, just asshownin Fig. 12-25,doeshavesomeadvantages.For one, there
areonly two amplifiers in the signal path to contributenoiseanddistortion,
and these can often be part of surroundingcircuitry and not specifically
"charged"to the filter. The L-C networkscanbe easyto tune, which may be
necessarywith the higher-orderfilters. Finally, the componentvaluestendto
be similar in magnitudeunlike the active Chebyshevfilter describedearlier.
On the minus side, the inductorsare susceptibleto hum pickup from stray
magneticfields and thereforeshould be of torroid or pot core construction
and kept away from power transformers. Also, it is conceivable that
nonlinearities in the magnetic core could contribute a slight amount of
distortion, so relatively wide air gaps within the core should be used.
lnductor size and Qare not much of a problembecausethe sectionresonant
frequencieswill be in the high audio range.

In actually building such a filter, accurateelementvaluesare crucial;
2.5% for fifth order, 1% for seventhorder, and O. 5% or better for ninth
order. This is normally accomplishedwith an impedancebridge, a bunchof
polystyrenecapacitors,anda supplyof ferrite pot coresandmagnetwire. The
pot coresusually have tuning slugs that simplify the task of getting exactly
the right inductance,and appropriateparallel combinationsof two or three
capacitorscan usually be determinedeasily. Typically, the parallel resonant
form will be preferredsince it has fewer inductors.

An active implementationof the filter using only op-amps,resistors,
and capacitorsis alsopossibleandstraightforwardto derivefrom the passive
L-C circuit. Whereasthe Sallenand Key circuit studiedearlier is a contrived
form that just happensto have the sameresponseas a resonantR-L-C low-

Page 418


passsection,impedanceconvertersare normally usedfor activeelliptical filters.
An impedanceconverteris an activecircuit that in effectconvertsonetype of
passivecomponent,suchas a capacitor,to anothertype, suchas an inductor,
by meansof phaseshifting. A gyrator, for example,doesjust that; connecta
capacitor across its ourput terminals and its input terminals have the
frequency-phasecharacteristicof an equivalentinductor. A negativeimpedance
convertershift things just 90° insteadof 180°andthus canmakea resistoract
like an inductor in a suitably designedcircuit. While these circuits are
interestingto study, their theory is beyondthe scopeof this discussion.

The negativeimpedanceconverter(NIC) is very easyto apply to theL-
Celliptical filter circuits given earlier, however. Figure 12-26A showsthe
seriesresonantform of aseventh-orderelliptical filter adaptedto a NIC active
circuit. In effect, the phaseof everything has been shifted 90° so every
inductor becomesa resistor, every resistor becomesa capacitor, and every
capacitorbecomesa "frequency-dependentnegative resistor" implemented
with a negativeimpedanceconverterand two capacitors.Fig. 12-26Bshows
the same circuit with "practical" element values included. These were
calculatedfor a lO-kHz cutoff from the Table 12-2 entries for a seventh-
order, 0.28/60-dBfilter. First, an impedancescalefactor is determinedusing
Z = 1/6.283FC, where F is the cutoff frequency and C is a convenient
capacitorvaluein farads.For bestresults,chooseC so that Z is in the 5K to
20K range. For this example,2,200 pF gave an impedancescalefactor of
7,235. Valuesfor the remainingcomponentsaresimply the impedancescale
factor times the correspondingelementvaluesfrom the filter table. Figure
12-26Cshowsthe actualactive filter circuit. Most of the resistorvaluesare
simply copied from the elementvalues in Fig. 12-26B. The two 499K
resistorsare includedto providea pathfor the amplifier biascurrentandalso
give the circuit accurateresponsedown to de. The 4.99K resistorsin the
negativeimpedanceconvertersmerelyneedto bematched;their actualvalue
doesnot affect the response.

Oneof the big advantagesof this circuit is that all of the capacitorsare
thesamevalue! Of course,the resistorsturn out to bestrangevalues,but it is
mucheasierto find precisionresistorswith strangevaluesthancapacitors.In
practice,the circuit impedanceis usually adjustedso that the capacitorsare
somestandardvalue(suchas 2,200pF here)which is easyto get. Onewould
typically purchaseseveraldozen5% capacitorsof this valueand selectthose
that fall within 1% of 2,200pF for use. Onepitfall of this circuit is that at
certainfrequencies,theoutputswingsof theNIC op-ampswill bethreetimes
the input signal amplitude. Thus, the input signal amplitude should be
restricted to 3 V peak to avoid severedistortion. Also, there is a 6 dB
passbandlossthat is madeup for somewhere,usually in theoutputamplifier.
Amplifier noise is not much of a problem becausethe NICs don't tend to
amplify noiseat the resonantpeaks.Note that the biascurrentfor amplifiers
AI, A3, and A5 plus that of the output amplifier passesthrough the two

Page 834

is toward controllers and player interfaces to instruments, I'd recommend substantial study in
analog circuits, electronic instrumentation and measurement, and sensors. And a course or two in
physics of materials wouldn't hurt either.

"Hobby work" is important too.

If one is not interested enough in instrument design to have spent and continue to spend free time
on personal instrument projects, a good job may still be possible but long-term creative excellence
is likely to be elusive.

Finally, unless you're going to work for one of the big 4 or 5 companies in this industry, its crucial
to understand economics in general and business economics in particular. They may call
economics "the dismal science" but that's only because if an entrepreneur doesn't understand it, the
result will be dismal. At least one course in basic business principles and perhaps one in marketing
may well be as important to one's success as all the previously mentioned stuff.

SONIK : If you were to move out of the music industry; What field would you like to work in?

HAL : Robotics is intriguing and before moving from North Carolina in 1986 I was an active
member of an amateur robotics club there. Accurately and gracefully controlling motors and
coordinating multiple movements is really a lot like sound and music synthesis. It's certainly a
much bigger market and also more focussed on useful results instead of style which sort of fits my

Another area of interest is the whole field of energy generation, efficiency, and conservation. One
of my contributions to the Kurzweil technology base has been higher efficiency linear power
supplies that produce less heat without switching noise. Doing more with less - of any resource
really - has always been an enjoyable challenge.

Yet another possibility I've given more than passing thought to is starting a small electronic gadget
company, perhaps with initial emphasis on bicycle accessories. Over the years I've developed
quite a laundry list of possible cool products that address specific problems but have never really
been able to pursue any of them. Might be a good "retirement" pursuit.

Additional Links:

Micro Technology Unlimited

NoteBender Keyboard

Kurzweil MIDIBoard

Jan 2002

Page 835

Musical Applications of
Hal Chamberlin

This expanded and revised edition provides in-depth
coverage of analog, digital, and microprocessor
sound and music synthesis. Written in non-
mathematical language, the techniques and concepts
are easily usable by musicians, computer users, and

New synthesis techniques, nonlinear waveshaping,
and Vosim and the fast Fourier transform are pre-
sented in understandable terms, and are supported
with program listings in BASIC and 68000 assembly

The background and historical material details the
most current advances in microprocessor tech-
nology. In addition, new analog synthesis techniques
and musical input devices as well as the latest linear
circuits and keyboard design concepts are explained.
There is an updated discussion of digital audio con-
version, inclUding a revised and expanded section on
digital synthesis techniques.

An entirely new section examines the practical ap-
plication of synthesis theory in actual synthesis prod-
ucts, including professional and studio equipment,
novelty products using modern synthesis tech-
niques, and sound generation circuits.


" ... this bookis a milestonein
microcomputerhistory. Its publica-
tion marksthe progression-from
noveltyto seriousinstrumentsof
ofsmall computersystems."BYTE

"Hal Chamberlin'sbook. ..
providesan excellentandcom-
prehensiveinsight into the
theoreticalandpractical useof
microprocessorsin digital sound
andmusicsynthesis.The bookwill
appealnot only to generalreaders
wishing to acquaintthemselves
with an overviewof the micro-
but also to the specialistalready
involvedin this area." SOUNDS



ISBN: 0·8104·5768·7

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o 8126245768 9

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