Music Synthesis Patents

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

• Moog, Signal Generator
  for Electronic Musical Instrument, Employing Variable Rate
  Integrator
• Yamaha, Waveform Converter for
  Use with an Electronic Musical Instrument and Capable of
  Controlling the Duty Factor of a Rectangular Wave Tone Signal
• Yamaha, Linear Voltage-Controlled
  Saw-tooth Oscillator
• Yamaha, Voltage-Controlled Oscillator
• Yamaha, Voltage-Controlled Type
  Oscillator

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

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Last modified 12/25/05
Maintained by Aaron Lanterman

lanterma@ece.gatech.edu