It should be horrid and jarring, but oddly enough it is really beautiful to listen to, in an eerie, "wrong" kind of way. Here is Dehumanized by Disturbed, reversed. http://www.youtube.com/watch?v=tggt_p9UHNw&feature=related A link of the actual song, just for fun http://www.youtube.com/watch?v=hWygwfE2Gww&feature=related
Just a couple of months ago in a local bar I saw the lead singer in a famous old rock band now obscure, so obscure I've forgotten the name, sing one of the band's familiar hit tunes backwards - like a tape recording played backwards. Apparently the stunt was a product of many long nights on the bus. It sounded OK, actually. There's a singer around somewhere who sings the Star Spangled Banner backwards. John Fahey was known for reversing tunes he had composed or sounds he had recorded, and composing with the reversals. See the album "Requia". Bach, famously and profoundly, and many other classical composers, reverse phrases and progressions (and invert them, etc).
