This has gone out of fashion but it used to be fun in the era of the turntable to slowly rotate your records backwards by hand and try to find hidden "messages" in them.

Check this lot out: http://jeffmilner.com/backmasking.htm

i remember this. Personally, i don't believe backmasking exists unless the forward part is jibberish. i know some bands did/do it on purpose for fun but as for "Stairway to Heaven" and other songs that don't have the jibberish part, i think it's all imagination. Then again, if you speak any xc post onto tape and play it backwards, you'll hear "xc has come for your daughters beware".

One thing that did exist- but not as sinister as the backwards music- was etchings in the end grooves on vinyl albums. Some artists had messages or fun scribblings in the grooves. i know John Lennon did it, he'd sign "Winston O'Boogie" or "Love ya, Yoko" or something similiar. Jimi Hendrix and Neil Young did such things, i believe, probably many more artists, too. No tonearm needles are damaged while hunting for these messages.