Backmasking

Backmasking is a recording technique in which a sound or message is recorded backward onto a track that is meant to be played forward. Backmasking is a deliberate process, whereas a message found through phonetic reversal may be unintentional.

Backmasking was popularised by the Beatles, who used backward instrumentation on their 1966 album Revolver. Artists have since used backmasking for artistic, comedic and satiric effect, on both analogue and digital recordings. The technique has also been used to censor words or phrases for "clean" releases of explicit songs.

Backmasking has been a controversial topic in the United States since the 1970s and popular during the 1980s and 1990s, when allegations from Christian groups of its use for Satanic purposes were made against prominent rock musicians, leading to record-burning protests and proposed anti-backmasking legislation by state and federal governments.

In 1877, Thomas Edison invented the phonograph, a device allowing sound to be recorded and reproduced on a rotating cylinder with a stylus (or "needle") attached to a diaphragm mounted at the narrow end of a horn. Emile Berliner invented the familiar lateral-cut disc phonograph record in 1888. His design overtook the Edison phonograph in the 1920s, partly because Berliner's patent expired in 1918, leaving others free to use his invention.

In addition to recreating recorded sounds by placing the stylus on the cylinder or disc and rotating it in the same direction as during the recording, one could hear different sounds by rotating the cylinder or disc backwards. In 1878, Edison noted that, when played backwards, "the song is still melodious in many cases, and some of the strains are sweet and novel, but altogether different from the song reproduced in the right way". The backwards playing of records was advised as training for magicians by occultist Aleister Crowley, who suggested in his 1913 book Magick (Book 4) that an adept "train himself to think backwards by external means", one of which was to "listen to phonograph records, reversed". In the movie Gold Diggers of 1935, the end of the dancing pianos musical number "The Words Are in My Heart" is filmed in reverse motion with the accompanying instrumental score incidentally being reversed.

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