Sidechain Timing Calculator

Release Shape is captured as an input but the engine explicitly discards it (it's read and then intentionally ignored in the calculation) — the millisecond math for cycle length, hold, and release is purely a function of BPM, beat division, attack time, and hold percentage. The dropdown exists to flag a real mixing consideration: an exponential release curve tends to sound smoother than a linear one at the identical calculated release time, but that's a perceptual difference your compressor's curve setting handles, not something this timing math models.

Release Time is calculated as cycle length minus attack time minus hold time, and the engine clamps that result to a minimum of zero instead of allowing a negative value. In practice this means the compressor would be engaged (attacking or holding) for the entire cycle with no time left to release before the next kick hits — a sign your attack or hold percentage is set too aggressively for the chosen beat division at that tempo.

BPM sets the underlying quarter-note length in milliseconds (60,000 divided by BPM), while Beat Division multiplies that base length down — a full multiplier of 1 for quarter notes, 0.5 for eighth notes, or 0.25 for sixteenth notes — to set how often within each beat the pump cycle repeats. A faster (smaller) division at the same BPM produces more, shorter pumps per bar, which is why Pumps per Bar is calculated as 4 divided by that same division multiplier.

Duty Cycle is attack time plus hold time, divided by the total cycle length, expressed as a percentage — it's the fraction of each cycle where the compressor is actively pulling gain down rather than released and passing signal freely. A low duty cycle produces a short, punchy duck with plenty of open space between pumps, while a high duty cycle means the compressor spends most of the cycle engaged, giving a more constant, squashed pumping effect.