The Modulation Matrix

Route LFOs, envelopes and velocity to any destination, and a static patch starts to move.

Related

SynthesizerMoog modular synthesizerProphet-5Modern

The question

Why does a held note grow brighter, wider or unsteady? If every knob held one value, the sound would sit still. The modulation matrix answers one question: what pushes what?

How it works

A matrix connects sources to destinations, and the amount at each crossing is the depth. Common sources are LFOs, ADSR envelopes, velocity, key position, the mod wheel and aftertouch. Common destinations are pitch, cutoff, level, pan, pulse width and effect send. Depth can be positive or negative. One source may push several destinations, and one destination may sum several sources. Modular synths use patch cables; software synths reduce it to a table.

Settings and what you hear

Vibrato is an LFO on pitch, with small depth and fast rate. A filter wobble is an LFO on cutoff, and slowly it reads as breathing. An envelope on pitch gives a percussion-like fall; velocity on cutoff makes accents brighter. Too much depth drives a destination into its limit, where it sticks. When sources sum, leave headroom, or one will hide the other.

What to listen for

On a long note, decide whether vibrato moves pitch or level. Then hear whether the pad's brightness rises and falls in a cycle. Finally compare accent and soft notes and judge whether velocity is routed to cutoff. Naming the source and the destination is the point.

Common misconceptions

That modulation means adding an effect; that more sources always improve a patch; that negative depth and summed routes can be ignored, when they decide the final direction and amount.

Sources

• Gordon Reid, Sound On Sound Synth Secrets — modulation routing checked, not quoted
• Curtis Roads, The Computer Music Tutorial — modulation and control signals checked, not quoted

Used for fact-checking only; all prose is original.