Mixer

The mixer, is an electronic device for combining (mixing), routing, and changing the level, tone and/or dynamics of audio signals.

Schematics

 * There are a couple of mixer schematics at Scott Stites Synth DIY
 * Minimoog Mixer, Noise and Power supply
 * Digisound 80, 80-4 Voltage Controlled Mixer
 * Modules at Ken Stone's Modular Synthesizer includes a number of mixers

Furter reading

 * Electronic Music: Systems, Techniques, and Controls by Allen Strange, McGraw Hill College, 1983, ISBN 0697036022 or ISBN 0075232197, Chapter 11, Audio Mixing,p. 175
 * Part 4 - Step by Step Guide to Synthesis at www.digisound80.co.uk includes patching with a VCM