1. First take the layer that has your audio select it and go to – animation – keyframeassistant – convert audio to key frames. (note be sure the work area covers the duration of the song you would like to animate to)
2. turn off the audio layer so you don’t see it
3. select the layer that is going to be animated to this music and make a key frame on whichever parameters you choose, make sure that parameter is selected and that you have a keyframe on it, then select animation – add expression.
4. open the layer that has the audio levels drop the triangles down till you see slider
5. pickwhip from your expression to the audio layer and you can alter these numbers in the expression to your own taste.
hope this helps