Buss compression glues a mix and should be inserted during mixdown so its side effects shape mix decisions

A compressor on the master/stereo buss responds to the whole mix moving together, gluing diverse elements so they breathe as one and adding cohesion, gentle pumping, loudness, and tonal character. Because it acts on the full mix, it changes the apparent balance of every element at once and has side effects to manage: pumping and breathing when gain reduction is too deep, softened/dulled drum transients from fast attack, and tonal shifts. The key workflow point: insert it during mixdown, not only at mastering, so channel-level decisions are made with its effect in place; adding it late will shift the balance and force re-adjusting everything (a kick/snare dulled by late buss compression is a predictable outcome). Starting with it makes the mix come together faster, may need less compression on individual tracks, and reduces fader automation. Glue compression rarely exceeds ~1–3 dB of gain reduction; hypercompression (over-limiting that flat-lines the waveform) destroys dynamics and must be avoided.

Examples

Classic SSL/VCA-style buss compressor starting point: slow attack, fast/auto release, ~2:1–4:1 ratio, threshold for ~2–4 dB gain reduction — glue without obvious pumping or heavily dulled transients. A separate ‘client mix’ can add extra limiting to simulate mastered level but should be delivered apart from the mix intended for mastering.

Assessment

Explain the trade-offs of inserting buss compression at the start versus the end of a mix. You add it after finishing and the kick and snare sound dulled — why is that predictable, and why should the buss compressor be in from the beginning? Name two indicators that buss compression has become excessive (hypercompression).