Keyboard follow routes note pitch to the filter so higher notes open the filter more

Keyboard follow (also called keyboard tracking) is a modulation routing that scales a parameter — most commonly filter cutoff — by the pitch of the note played. With filter keyboard-follow engaged, higher notes push the cutoff higher, so the upper range of a patch stays proportionally bright instead of sounding progressively duller as pitch rises. This keeps a chord voice’s timbre consistent across its playing range and prevents high voicings from being swallowed by a fixed filter setting. The amount is adjustable: full tracking makes brightness scale one-to-one with pitch, partial tracking (e.g. a mid setting) applies a gentler correction. It is a general subtractive-synthesis primitive, independent of genre.

Examples

In Diva, engage the Kybd (keyboard follow) slider at ~65 so the notes played affect the filter. Play a low chord then a high chord: with tracking on, the high chord stays proportionally bright; with tracking at 0, the high chord sounds duller relative to the low one because the cutoff is fixed.

Assessment

Explain what audibly changes across a synth’s pitch range when filter keyboard-follow is raised from 0 to full. Why does a patch designed at one octave often sound wrong two octaves up without keyboard tracking?