image courtesy of Benjamin Ward

The Matrix-12, truly one of the "Monsters" of programmable analog synthesizers. It is basically two complete Oberheim Xpanders hooked up to a velocity-sensitive (including release velocity), pressure-sensitive (there were some early Matrix-12s that did not have pressure-sensitivity), 5-octave, 61-note (C-C) keyboard. With 24 oscillators (two VCOs per voice) it can be set up as a 12-part monophonic or a 6-part polyphonic multi-timbral synth. The front panel is exactly like the Xpander, except for one button that switches between voices 1-6 and 7-12.

Like the Xpander, each voice consists of 2 VCOs (triangle, saw, pulse, or noise, VCO2 could be synced to VCO1), a multimode VCF (low-pass, band-pass, notch-pass, high-pass and four "combination" filter modes), and 4 VCA's (in line one after each oscillator and two after the VCF). FM of VCO1 and the VCF is possible via VCO1. The filters can also be set as 1-pole (6dB/octave), 2-pole (12dB/octave), 3-pole (18dB/octave), or 4-pole (24dB/octave). All oscillators and filters can be tuned by a handy auto-tuned routine. In addition to this basic synth engine, the Matrix-12 has a number of separate modules that can be inserted in any modulation path. These include (10) LFO's with basic waves plus sample-and-hold and random functions, 6 tracking generators, 6 ramp generators, two lag processors (they do not necessarily have to be used for portamento), and 1 additional global LFO to be used with the Mod Wheel.

Unlike the Xpander, the Matrix-12 does not have individual outputs (although they were available as an option, which involved replacing a side panel to make room for the connectors) or CV/gate inputs.

[from The A-Z of Analogue Synthesizers , by Peter Forrest, published by Susurreal Publishing, Devon, England, copyright 1994 Peter Forrest]