Virtual Analog Synthesis and Effects

This appendix introduces virtual analog audio synthesis and effects. The term ``virtual analog'' refers to any digital signal processing system that is designed to simulate an analog signal processing system. Analog systems are typically built using resistors, inductors, capacitors, diodes, and transistors, so one approach to virtual analog is to ``digitize'' each element; an example of this approach is wave digital modeling, introduced and discussed in Appendix Q. Another approach to virtual analog is to formulate a digital system that presents the same controls (and control-responses) as the analog system to be digitized. This appendix is primarily concerned with this latter approach.

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Subsections

• Subtractive Synthesis
• Phasing
  • Phasing with First-Order Allpass Filters
    • Classic Analog Phase Shifters
    • Classic Virtual Analog Phase Shifters
  • Phasing with 2nd-Order Allpass Filters
    • Allpass Phaser Architecture
    • Allpass Phaser Parameters
    • Allpass Phaser Notch Distribution

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written by Julius Orion Smith III
Julius Smith's background is in electrical engineering (BS Rice 1975, PhD Stanford 1983). He is presently Professor of Music and Associate Professor (by courtesy) of Electrical Engineering at Stanford's Center for Computer Research in Music and Acoustics (CCRMA), teaching courses and pursuing research related to signal processing applied to music and audio systems. See http://ccrma.stanford.edu/~jos/ for details.