Sound engineers will tell you that generally it’s best to compress the signal at the point where the least amount of bass is present (at least that’s what I’ve heard). Think of a thumping bass line. The bass frequencies carry a lot of energy, and a compressor responds to changes in the level of the bass frequencies.

This can cause the high-frequency instruments to seem to stand out in the overall mix. By adding compression where there is the least amount of bass, you can keep the compressor from drawing out too much of the high frequencies. To the ear, this will keep the levels a little more stable and prevent high frequency instruments from sounding louder than you intended. This is a good time to start automating plug-ins, getting your compressor to kick on when and where you want it to.