Sidechain-pump has two roles: functional masking-avoidance between kick and bass, and aesthetic pump as a genre signature

Sidechain-pump ducks a sustained voice (bass, pad) on each kick so the kick punches through and the track breathes. The source separates two roles: functional — carving masking-avoidance between kick and bass so the bass dips exactly when the kick hits and both are heard; and aesthetic — the audible pump is a genre signature, the pulsing swell of house/EDM/dub-techno. Whether it reads as ‘invisible glue’ or ‘obvious pump’ is a depth/release choice, not on/off: deeper and longer ducking gives a more obvious pump. The feel is a fast duck plus a release that pumps back up in time with the tempo, about one 8th or 16th note, so it locks to the groove rather than clicking (too fast) or staying ducked (too slow).

Examples

Strudel: .duck('bd*4').release(0.1) ducks the bass to the kick with an ~8th-note release at 120 BPM. Shallow depth for glue; deeper depth for an audible pump.

Assessment

Explain sidechain-pump’s two roles. What parameter controls whether it reads as glue or obvious pump, and what release-time guideline keeps it locked to the groove?