Pretty self explanatory. What's the longest song you've played on Audiosurf? For me, it's "Octavarium" by Dream Theater which clocks in twenty four minutes long. (Well what can I say. I was stuck at home with a kidney stone and there was nothing to do. I had do something to kill time) I also plan on posting a run of the song on Youtube when I get a chance to record it.
When The Water Breaks by Dream Theatre. about 17 minutes.