Compressor timing from BPM
Release times that let the compressor recover in step with the music, and a starting attack range for the source you are working on.
Slow enough to let consonants through — clamp the front of a word and the singer stops sounding present. The body behind the transient is what you are levelling.
Values in the practical release window for Vocal are lit; the rest are shown for completeness. Hz is the reciprocal — 1000 / ms — useful when you want to know what a release time does to a low frequency passing through it.
How to read this
The arithmetic is trivial — quarter = 60000 / BPM, dotted ×1.5, triplet ×2⁄3 — and it is not the interesting part. What matters is that a compressor releasing in step with the music breathes with the part instead of against it. Release too fast and you hear the gain moving between hits; too slow and the compressor never recovers, so it holds everything down uniformly and the groove flattens.
Attack is a different decision, made by the source rather than the tempo. A fast attack catches the transient and takes the front off the sound; a slow one lets the transient pass and compresses the body behind it. That is why an attack that flatters a vocal will strip the life out of a drum buss.
An honest caveat about optical compressors. OPTO Comp has no attack or release controls, and neither does the hardware it models. In an optical circuit those times are not settings — they are what the photocell does. Recovery is program-dependent: fast at first, then a long tail, and different after a loud passage than after a quiet one.
So these numbers are not settings to dial into an opto. They are a way to hear what the circuit is already doing — a reference for how long a musical recovery lasts at your tempo, so that when you watch the reduction needle you know whether it is breathing with the part or lagging behind it. On a VCA or FET compressor, where those controls do exist, the numbers are a starting point rather than a reference.