Compressors - these are hard pedals to describe. someone once told me "if you don't hear it, it's working?" Basically what they meant is that it should just squeeze things in a way that puts the notes more clustered together. Making your tone a bit smoother and also if you use a distortion or Overdrive you should be able to make the not ring a tad longer! The mix feature is great because you can back some of the compression off, which in the world of compressors is a great thing!