Richard Williams once found out that the other genius animator Milt Kahl doesn't listen to music while he is working. Kahl explained: "I am not smart enough to focus on animation and listen to music at the same time." Since then Williams told the world of animators not to listen to music. :-)
Sometimes I find it hard to work with music but during the night work music helps to forget about sleeping and in some cases it inspires me. Mostly it depends on the type of project you are working on. I know that Mozart helps to make a research.
Here is some info about great animator - Richard Williams. He is a Canadian animator. He is best known for serving as animation director on Disney/Amblin's Who Framed Roger Rabbit and for his unfinished feature film The Thief and the Cobbler. He was also a film title sequence designer and animator; his most famous works in this field included the title sequences to What's New, Pussycat? (1965), title and linking sequences in The Charge of the Light Brigade (1968). He also animated the eponymous cartoon feline for two of the later Pink Panther films.