COMPRESSION is used on almost every piece of recorded music we listen to. The idea of compression in recorded music is to level out the dynamic range of a sound by removing loud jumps in level.
For guitar players, it can be used to boost your signal, increase sustain for soloing, create the snappy attack that you hear on country and funk guitar parts, or even bring out a fingerpicked part.
Imagine someone manually controlling your volume for you, so every time you hit a note above a set volume level (threshold), they turn it back down by a percentage. That’s essentially how a compressor works. Studio compressors usually feature more controls than their stompbox counterparts, which often only have a few knobs. Attack usually governs how quickly the signal is attenuated (the reduction of amplitude) after the volume reaches the threshold level, and sustain controls how much the signal is turned down by.
Once you’ve compressed your signal, you’ll need to turn the whole lot back up again, and that’s what your level/output control is for. The result is a much smoother signal with noticeably less dynamic range, and a greater consistency in volume.