The compressor belongs to the dynamics processors. It reduces the dynamics and thereby increases the loudness. There are different setups, which is why there are different control behaviors and sound characteristics. The four compressor types are the tube compressor, FET compressor (field effect transistor compressor), opto compressor (optical compressor) and the VCA compressor (voltage controlled amplifier compressor). Compressors are used in the song process in production, recording, mixing and mastering.