I think everybody heard about the rumors that in commercial music
are satanic messages hidden. And when you play the sound backwards
the real sense will turn out. Jeff Millner has a webpage where you can
listen to some tracks, forward and backward. He calls it backmasking.
The best example is »Baby one more time« from Britney Spears:

Forward: »With you I lose my mind give me a si.«
Bachwards: »Sleep with me I’m not too young.«

But that’s pretty hard. Others just made funny things, like Pink Floyd.
Forward you don’t understand a word, but backmasked: »Congratulations.
You have just discovered the secret message. Please send your answers
to old pink, care of the funny farm, Chalfont.«

But check them out yourself, there are a lot more samples >>