Comb filter

ATMOSYNTH built-in module

A filter tuned to a pitch rather than set to a cutoff. It delays the sound by exactly one period of that pitch and adds it back to itself, so everything at the pitch and its harmonics reinforces and everything between cancels — a whole row of peaks and notches at once, which is the sound of a short room, a cardboard tube, or a plucked string depending on how much of it goes round again. Resonance is how much: near one it rings on into a pitch of its own long after the sound that started it, and below nothing the feedback is subtracted instead, which shifts every notch by half a spacing and leaves the hollow, woody sound an octave below where you would expect it. Damping takes a little more of the top off each time round, so the ring dies from the treble down as a string does rather than all at once. Pitch is an input as well as a knob and Pitch amount is how far, in cents — an LFO patched in is a flanger you wired yourself — and Key tracking moves the tuning with the note played, which needs the note routed here: at one the comb rings in tune with whatever is played through it. This module carries code, for the one thing the node vocabulary cannot do: a comb's delay is one divided by its pitch, and nothing in that vocabulary divides.

What this module is made of is not shown here. Fork it into the editor to see for yourself.