In what is considered to pretty much be one of the animation bibles, The Animator's Survival Kit declares that animation is concentration. Many people listen to music while they draw, but Milt Kahl considered this counter-productive since it divides concentration and that you are not fully investing your brain into what you are doing.
While I've had many discussions with others on this topic before, everyone's responses have varied. I've concluded that it all depends on the individuals' work ethic; several animators have stated that they listen to the Animation Podcast while they work, while others like Milt Kahl find it too distracting.
I find myself perfectly capable to draw without having to rely on music, but it is a nice inspirational boost to get into my creative groove and engage into what I'm doing. Listening to a certain genre at a low volume is also very nice when designing a particular character or trying to convey a specific attitude/mood. The music might get distracting though once I'm locked in, so at that point I just shut it off. Otherwise, I just let it keep going. To me, music is the biggest success when it is able to get me in the zone and I eventually forget that it's even playing.
From The Animator's Survival Kit