I recently heard that if you play Stairway to Heaven by Led Zeppelin you'll hear "Oh, here's to my sweet Satan..." (See http://www2.memlane.com/jmilner/stairwaybackwards.htm)

Now I wonder if someone would be interested in developing a component to foobar2000 which play songs backwards (just for fun) if that's not too hard, since I don't have the knowledge to do it myelf

Already suggested at least once. Just to reiterate, it would either require full decoding and buffering first, or seeking to near the end of the file and decoding whole chunks from the end to the start and playing them backwards in turn. Either way, it won't be pretty.

I see. Thanks for the answer.

There's a freeware audio editor called Audacity that can import audio files and play them backwards.

http://audacity.sourceforge.net/