Was trying to think of when you might want to watch a cursor moving through a sound file.
For any reason besides "we at Soundcloud needed a gimmick to keep your attention while you listen to music here."
Perhaps if the wave had an interesting shape and the sound was somewhat intriguing and there was some obvious, necessary correlation between the two.
So I made this [Vimeo] as an experiment. [Embedded version]
Had been wanting to post that bit of electronic music but it needed something more. This might be it.