A technique claimed to be used in some rock music (especially heavy metal) in order to convey secret, destructive messages. Some conservative Evangelical Christians have claimed that various words and sentences in rock music songs indicate Satanic messages when played backwards. Reversed rituals are a traditional aspect of black magic spells.
The belief in backward masking rests largely on an understanding of subliminal perception, the ability of the brain to take in and store information quite apart from any conscious realization that the information is being received. While a certain amount of subliminal learning seems possible, the idea of backward masking carries the idea to an extreme by suggesting that the brain can receive a coded message and unscramble it. While many Evangelicals believe that Satanism is a real force among contemporary youth, only a few have paid attention to the highly dubious claims concerning backward masking.
Aranza, Jacob. Backward Masking Unmasked. Shreveport, La.: Huntington House, 1983.