I used the search function (!) but couldn't find a related thread on this. Will compressing kill the fretless sound? And if not, which pedal or other kind of unit will suit the fretless best?
I have never liked anything more than very light compression on a fretless. Usually I have none. It kills the organic quality of the sound. If you do use compression, I would try a ratio of no more than 2:1 and no more than 4 db of gain reduction with a slow attack and release.