Incorrect compressor attack and release settings cause pumping, where the level audibly rises and falls with the music

Pumping is a compressor artifact in which the overall level of a mix audibly increases and then decreases as the compressor releases between transients — each time the dominant instrument starts or stops, it pumps the level up or down. It arises from release settings interacting badly with the program’s dynamics. Compressors that work best on full program material have smooth, slow release times to minimize pumping.

Examples

Glenn Meadows uses a 1.15:1 ratio at –20 to –25 dB threshold to get into the compressor early — gaining 3–4 dB of average level without an audible compression effect or pumping.

Assessment

Define pumping in a mastering context and identify which compressor parameter most directly causes it.