It depends, but usually when I'm grinding offline or in KL, I play with ingame music turned off and listening to a playlist in Spotify, that I choose depending on my mood (the most usual to play with Kano online is some HxC punk or r&r as it fits him so well and encourage the agressive risk/reward playstyle jaja). I never turn sound effects off and, generally speaking, I play my music at a low/medium volume as if it was ingame music.
However, sometimes I just play with all the ingame sound on.