The craziest thing I've ever played on an instrument, at least for an audience, would be one of the four parts in an arrangement of the above song for a classical guitar quartet. The guitar version of this is actually crazier, due to the different sound of a classical guitar compared to a full orchestra. I've done some rock, blues, and if Nightwish counts, metal as well, but this song is, frankly, much crazier than anything else I've played in concert on an instrument. I spent my first year of college as a music major, so I did some pretty interesting things. I wish I had access to the recordings we made of the Vocal Jazz Ensemble, which I was also a part of. That's the group that I was in that did the craziest music I've ever done, but the question was instrument, not vocals, so whatever.