Critics of rock and roll songs (and of Led Zeppelin in particular) have alleged<43> that a backmasked message is recorded into "Stairway to Heaven." The message, which allegedly occurs during the middle section of the song ("If there's a bustle in your hedgerow, don't be alarmed now..."), is purported to contain Satanic references:
Oh here's to my sweet Satan.
The one whose little path would make me sad, whose power is Satan.
He will give those with him six six six.
There was a little toolshed where he made us suffer, sad Satan.
The controversy originated from a prominent Baptist, who, in 1982, preached on the radio that "Stairway to Heaven" contained subliminal backward messages. This theory was later primarily advanced by Michael Mills, Jacob Aranza, and Jeff Godwin, who offered detailed analyses asserting the existence of hidden meanings within both the "backwards" and actual lyrics. In 1982, the Consumer Protection and Toxic Materials Committee of the California State Assembly held a hearing on backmasking in popular music, during which "Stairway to Heaven" was played backwards. William Yarroll, a self-identified neuroscientist, also claimed that "Stairway to Heaven" contained a message when played backwards. Various versions of the alleged message exist.
The band itself has for the most part ignored such claims; for years the only comment came from Swan Song Records which issued the statement: "Our turntables only play in one direction—forwards". Led Zeppelin audio engineer Eddie Kramer confirmed this, calling the allegations "totally and utterly ridiculous. Why would they want to spend so much studio time doing something so dumb?" Robert Plant expressed frustration with the accusations in an interview: "To me it's very sad, because 'Stairway to Heaven' was written with every best intention, and as far as reversing tapes and putting messages on the end, that's not my idea of making music."
An informal experiment by scientist Simon Singh suggested that listeners only hear the message after prompting.
http://en.wikipedia.org/wiki/Stairway_to_Heaven#Backmasking_controversy