My demo track was a live version of The Yellow Jackets' "Wildlife" from "Live Wires". It may have been in poor taste because it is quite long (9:25) and starts off with a lot of percussion antics, but I ended up writing it down for someone in pretty much every room it played. Probably not audiophile approved, but fun to listen to.
One speaker maker, who shall remain nameless, initially refused to cough up the disc. I really had to bargain my way out of there.