Okay, if you get this one you're good.
A few pertinent comments before you listen to the mp3:
1. It's a very short -- barely a minute and a half -- orchestral piece and it's thrilling.
2. It is, deliberately, a sideways re-write (down to the identical closing organ chord) of a very famous classical work that everybody on the planet would recognize.
2. The first time anybody but a handful of the composer's friends and colleagues heard it was in 1993, when the score was first recorded and premiered on CD. The piece itself had actually been written nearly two decades earlier, though.
3. I reviewed the album at the time in the Magazine Formerly Known as Stereo Review, and I got a major fact wrong.
4. Whatever you do, don't listen to it on ear buds -- plug it into your stereo and PLAY IT LOUD!!!! Or if you have good computer speakers, at least, crank it that way.
5. What are you waiting for?
In any case, a coveted PowerPop No-Prize will be awarded to the first reader who correctly identifies the thing.