Compression is used on the tracking side to get a better S/N ratio. It does not have to be heavy 4:1 and high t/hold maybe. It can also be used as an effect for the part. When Im tracking I use soft compression on the BD and the SN mainly as a limiter, On the vocal I use a bit more 4:1 so it hit's the louder parts, Bass gtr I use about 8:1 with a high t/hold depending on style. It is very useful to use pre and post recording, if you think it might be too much, then back it off. Experiment and see what happens. Mark..