Music Synthesis Patents Collection

This a collection of patents related to music synthesis (and occasionally processing and other things). It is obviously not meant to be exhaustive; it just contains patents I found interesting for one reason or another at a time I was looking through patents. The first patents I added here were manually combined into a single PDF file from the single-page TIFFs from the U.S. Patent site. I've since discovered pat2pdf.org.

Voltage Controlled Filters

Moog, Electronic High-Pass and Low-Pass Filters Employing the Bass to Emitter Diode Resistance of Bipolar Transistors - yup, that's the one!
Moog, Wide Dynamic Range Voltage Controlled Filter for Electronic Musical Instruments - not sure what this might have been used in
Hammond Corporation, Voltage Controlled Filter - 4-pole with negative feedback, uses FETs as variable resistors. Anyone know of any products where this might have been used?
Yamaha, Voltage Controlled Filter - Uses a diode ring as a variable resistor, demoed with a Sallen-Key topology. This the basis of the GX-1 filter.
Oberheim/Rossum, Circuit for Dynamic Control of Phase Shift - Single-pole filter via an OTA (similar to the ARP patent), referenced by the SSM2040 datasheet
Rossum/Dow, Lowpass Filter with Electronic Control of Cutoff and Resonance - refered by the SSM2044 datasheet
ARP, Frequency Sensitive Circuit Employing Variable Transconductance Circuit - Single-pole filter via an OTA (similar to the Oberheim/Rossum patent)
ARP, N-Pole Filter Circuit Having Cascaded Filter Sections - Cascade of OTA-based single-pole sections
ARP, Dynamic Filter - 4-pole, uses Norton (current in/voltage out) amplifiers
General Electric, Voltage Controlled Electronic Filter - not written for a musical application, but still potentially interesting

Voltage Controlled Amplifiers

Blackmer, Multiplier Circuits - the classic exponential-control "Blackmer" cell, used in THAT (aka DBX) chips
Excellent EDN article on Gain Control, which contains a much clearer description of how the Blackmer cell works

Voltage Controlled Oscillators

General Variable Impedance Circuits

These are interesting. I wonder if any of these designs were made into voltage-controlled impedance ICs? If so, they would make the process of turning a fixed filter into a VCF pretty easy.

Pioneer, Electronic Impedance Service for Providing a Variable Impedance
Dolby, Electrically Variable Impedance Circuits
Hitachi, Variable Impedance Circuit
Yamaha, Variable Resistance Circuit
Katakura, Electrically Variable Impedance Circuit

Chorus Effects

Roland, Device for Producing Chorus Effects
Moog, System for Producing Chorus Effect

Miscellaneous

Yamaha, Generator for Generating Control Voltage Waveform

Last modified 12/25/05
Maintained by Aaron Lanterman

lanterma@ece.gatech.edu