BTW, classical music doesn't fare too well through Audiosurf, can create some fairly flat tracks. You can adjust this to make the track more dramatic with the [as-steep] tag, there's an addon called 'Yet Another Audiosurf Player' (YAAP) which'll do this for you (search for it).
Or you can manually edit the ID3 tag of the music track and add '[as-steep]' after the title.