Backmasking (also known as backward masking)[1] is a recording technique in which a sound or message is recorded backward on to a track that is meant to be played forward. Backmasking is a deliberate process, whereas a message found through phonetic reversal may be unintentional.
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You dumbass it's a different thread.
http://jeffmilner.com/backmasking/stairway-to-heaven-backwards.html