Backmasking, a recording process that allows sounds or messages to be heard when playing a song backwards, has been used since the 1960s.
This is a deliberate process, rather than aleatory sounds that are heard when songs are played in reverse, which may or may not have any meaning. These messages were intentionally recorded backward onto a track that is meant to be played forward.
Click through the gallery and get to know the hidden messages artists added to their songs.