Compressor
An effects device that reduces the dynamic range of an audio signal by evening out level differences.
What it means
A compressor is a device or plug-in that reduces the level of signals above a set threshold, while quieter signals pass through unaffected. This narrows the gap between the quietest and loudest parts of an audio signal.
Musical use
Key parameters are threshold, ratio (how strongly the level is reduced), attack (how fast it kicks in) and release (how fast it lets go); together they decide how audible the effect becomes. Compressors even out vocal or instrumental recordings, tighten drum sounds, or, in mastering, make a track sound consistently loud next to others. A compressor differs from a limiter, which uses an extremely high ratio to effectively cap peak levels, and from a noise gate, which conversely mutes quiet signals below a threshold.
Performance practice
Use compression sparingly, and compare the processed and unprocessed signal directly to check whether the dynamics still feel alive — over-compression makes music flat and tiring to listen to.