In premiere 6.5, you have to hit the little triangle button on the audio track to expand it as you would any other track. Then just hit the + key or slid the slider under the navigator to zoom in.
In 1.5 you should have the wavform at your disposal to begin with. You can enlarge it by clicking the space between the bottom of the audio track you music is on and the one below it, likely the master track. To zoom, just click the timeline and press the + or - key to zoom in and out respecivly. You can also slide the edge of the bar just above the timecode on the timeline left or right to zoom.
I'm sure 2.0 would be somewhat similar with the + and - keys. Just click around the timeline window and see what does what.