Download ECE/MUSIC 4

ECE4803B: Theory and Design of Music Synthesizers
Instructor: Aaron Lanterman
Credit: 3-0-3
Corequisite: ECE3041
This course is currently being offered for the first time in the Spring 2006 semester.
Lecture movies, homeworks, and other tidbits are available for viewing at
users.ece.gatech.edu/~lanterma/ece4803. This course has created quite a stir among the
do-it-yourself synthesizer community; I have received over two dozen e-mails from
around the world about them.
Prereq/coreq change from last proposal: The prereq for the first offering was
ECE2025 and (ECE3040 or ECE3710). I would like to change that to a co-requisite of
ECE3041. This will have a negligible change on the potential student body, as students
generally take 3041 the semester after they take 3040.
At the start of the semester, I handed out a survey to the Atlanta section asking about
certain classes. The results were as follows:
1 student had not taken and is not co-registered in 3041
2 students are co-registered in 3041
8 students had taken 304 and are co-registered in 3042
4 students had taken 3041, but are not co-registered in 3042
18 students had taken both 3041 and 3042
So, this change would only have affected one student. Basically, I want to make sure that
the students will have had some lab experience with oscilloscopes and other gadgets by
the time we get to the analog design project. Also, although the current offering has been
focusing on a traditional pencil-and-paper homeworks, I am also hoping to experiment
with a few small hands-on labs earlier in the semester in the Fall offering. I have been
reviewing Tom Brewer’s ECE3041 notes, and have a reasonably good sense of what
students will be familiar with at any given point.
Goal: This interdisciplinary course ties together threads in analog electronics, digital
signal processing, and applied physics using music synthesis the unifying topic.
Examples are drawn from 40 years of commercially produced hardware, with emphasis
on studying full schematics of real synthesizers and not idealized “textbook”
examples. This class is not about how to use any existing piece of equipment (although
students will gain insight that may help them better use their own gear). Instead, it
develops the skills and knowledge needed to develop new kinds of electronic
instruments.
Grading: Small laboratory/homework assignments (approximately one per week) (40%)
Practical hardware construction exercise (10%)
Analog hardware design project, due at end of semester (30%)
Involves proposal, progress reports, and final report,
as well a working delivered product
Written in-class final exam (20%)
Text: Selected readings from papers, magazine articles, and book chapters; I am also
starting to put my notes into LaTex, which I hope to turn into a book at some point.
Outline:
The outline listed up to “transistor/diode ladders’ is based on lectures from this
semester’s offering; the material listed after that may be subject to change based on
experience from future lectures in this semester. I may not have time to get to the
physical modeling material this semester; next semester I will be able to move through
some of the earlier material more smoothly, which will allow more time for physical
modeling.
1. Intro: 40 Years of Music Synthesis (2 lectures)
2. Analog Synthesis
a. Modular analog synthesizer demo (1 lecture)
i. Modular approach vs. integrated approach
1. Basic VCO -> VCF -> VCA chain
ii. Voltage control
1. Envelopes
2. Low frequency oscillators
b. Review of op-amp circuits
i. Resistive circuits (1 lecture)
ii. First-order RC circuits (1 lecture)
c. Operational transconductance amplifiers (1 lecture)
i. Voltage controlled amplifier (VCA) example
d. Voltage Controlled Oscillators (VCO)
i. Sawtooth core (1 lecture)
ii. Triangle core (1 lecture)
e. Analog waveshaping
i. Saw->Pulse, Saw-> Triangle, Tirangle->Sin (1 lecture)
ii. Wavefolding (1 lecture)
1. Ken Stone/Serge Wave Multiplier
2. Buchla’s timbre generator
f. Voltage Controlled Filters (VCF)
i. Single-pole OTA-based VCF (1 lecture)
ii. Four-pole cascade with negative feedback (1 lecture)
1. Ex: SSM2040 in Sequential Prophet 5
iii. Properties of second-order filters (1 lecture)
iv. Sallen-Key VCF (1 lecture)
1. Vactrol-based (Ex; Buchla Lowpass Gate)
2. OTA-based (Ex: Korg MS-20)
v. State Variable OTA-based VCF (1 lecture)
1. Ex: Oberheim SEM, EML 101
vi. Transistor/diode ladders (1 lecture)
1. (Ex: Moog, EMS Synthi, Roland TB-303) (1 lecture)
g. Temperature-compensated voltage-to-current exponential conversion
3. Digital Synthesis
a. Limits of digital sample playback
b. “Virtual Analog”
i. Aliased and unaliased digital oscillators
ii. Conversion of analog filter topologies into digital forms
c. Additive synthesis
i. Analysis/resynthesis
d. Waveshaping/Chebychev polynomials
e. Frequency Modulation (FM) synthesis (ex: Yamaha DX-7)
f. Hybrid digital/analog synthesis (ex: PPG Wave, Sequential Prophet VS)
4. Physical modeling
a. PDE models
i. String/cavity models
ii. Traveling wave solutions
b. Digital waveguide implementations
c. Excitation models
i. Plucking
ii. Bowing (stick-slip)
iii. Blowing
d. Introduction to physical models with multiple spatial dimensions
Tentative readings and reference material:
Patents:
 3,475,623, R.A. Moog, Electronic High-pass and Low-pass Filters Employing the
Base-to-Emitter Resistance of Bipolar Transistors, 1969
 4,039,980, Y.Nagahama, Voltage-Controlled Filter, 1977
 3,805,091, D. Colin, ARP Instruments, Frequency Sensitive Circuit Employing
Variable Transconductance Circuit, 1974.
 3,969,682, D.P. Rossum, Oberheim Electronics, Circuit for Dynamic Control of
Phase Shift, 1976.
 3,924,199, A.R. Pearlman, ARP Instruments, N-Pole Filter Circuit Having
Cascaded Filter Sections, 1975.
 4,011,466, A.R.Pearlman and C. Gillette, ARP Instruments, Dynamic Filter,
1977.
Papers:
 R.A. Moog, “A Voltage-Controlled Low-Pass, High-Pass Filter for Audio Signal
Processing,” Preprint 413, 17th Annual AES Meeting, Oct. 1965.
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J. Chowning, “The Synthesis of Complex Audio Spectra by Means of Frequency
Modulation,” J. of the Audio Engineering Society, Vol. 27, No. 7, 1973; reprinted
in Computer Music Journal, Vol. 1, No. 2, 1977.
J. Lane, D. Hoory, E. Martinez, and P. Wang, “Modeling Analog Synthesis with
DSPs,” Computer Music Journal, Vol. 27, No. 4, 1997, pp. 23-41.
T. Stilson, “Alias-Free Digital Synthesis of Classic Analog Waveforms,” 1996
International Computer Music Conference, http://ccrmawww.stanford.edu/~stilti/papers/blit.pdf.
T. Stilson, “Analyzing the Moog VCF with Considerations for Digital
Implementation,” 1996 International Computer Music Conference, http://ccrmawww.stanford.edu/~stilti/papers/moogvcf.pdf.
J.O. Smith III, “Physical Modeling Using Digital Waveguides,” Computer Music
Journal, Vol. 16, No. 4, 1992, pp. 74-91,
http://ccrma.stanford.edu/~jos/pmudw/pmudw.pdf
Magazine Articles:
 N.A. Steiner, “Voltage-Tunable Active Filter Features Low, High, and Bandpass
Modes,” Electronic Design, Dec. 1974. (Clever design using diodes as variable
resistance elements)
 H.S. Malvar, Voltage-Controlled Integrator Sets Filter’s Bandwidth, Electronics,
July 1980. (OTA-based State Variable VCF)
 S. Franco, “Use Transconductance Amplifier to Make Programmable Active
Filters: The OTA Offers a Ten Octave Tuning Range by Using Predictable Vbeversus-Ic relashionships,” Electronic Design, Sept. 1976. (OTA-based State
Variable VCF)
 T. Orr, “Voltage/current controlled filter,” Nov. 1976. (OTA-based Sallen-Key
VCF)
Books (Selected Readings):
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H. Chamberlin, Musical Applications of Microprocessors, Second Edition, Sams,
1985.
P.R. Cook, Real Sound Synthesis for Interactive Applications, AK Peters, 2002.
C.R. Roads, The Computer Music Tutorial, MIT Press, 1996.
C. Dodge and T.A. Jerse, Computer Music: Synthesis, Composition, and
Performance, Second Edition, Wadsworth Publishing, 1997.
J.O. Smith III, “Physical Audio Signal Processing: Digital Waveguide Modeling
of Musical Instruments and Audio Effects,” draft online at
http://ccrma.stanford.edu/~jos/pmudw/pmudw.pdf.