For the last months, I'm using SoundCloud's API to create an application. I had several issues, that I managed to solve, and this one I'm going to show you is one of my favorite. The waveform that soundcloud generates for a song, looks like the one I attached to the post.
It's not bad, as long as you can integrate the gray mask with your application design. If you can't then you can start to scratch your head. I did. :)