I still care about music in MP levels as well, not just SP. Infact, most of the levels I start making are inspired by a tune of some kind, as I tend to think "what tileset could go with this tune?". Hearing a techno upbeat tune in a jungle level doesn't do it for me even if it's MP. And having a downbeat ambient tune in MP just doesn't do it for me either, not that I hate the music style, but it doesn't put me in the mood to play, for SP it's fine though. Upbeat tunes in SP can work, depending on the pace of the level itself.