I would like to ask another question, how do you time it? Like if it says "spread your wings and fly" in a song how do you get to where once it says that then your animation does that. If its confusing to understand what I said then I do understand and you don't have to answer.
If you'd like to animate just one part of a song, then you need Audacity to edit the song for that part. Then you import to Flash, drag it from the library and drop it anywhere on the screen, make the keyframes longer and you got some of the song. (confusing isn't it o.O)