Online I am more likely to listen to music (sometimes I will and sometimes I won't). In live poker, I prefer silence and to remain attentive to what is going on. I also don't want to miss any potential "audio
tells" my opponent(s) give off because I have headphones/music etc. When playing online games, there is no such danger in missing those tells because no one can "pick up on them" in online games. Perhaps that is one reason I am more likely to listen to music online than live. In live poker, I don't think music would distract me much if at all - but I prefer to focus on the moment and game instead.
If I do listen to anything, I like "poker music" to get me mentally motivated. Songs like John Cameron 4 O'clock Rumble, Kenny Rogers Gambler or even Motorhead Ace of Spades. Other times I just prefer classical music and calming things. Probably everyone will just listen to what kinds of music they normally enjoy.