The central feature of hidden messages in songs is that the listeners must do something (slow down the playing speed, play it backwards, listen carefully) to interpret the lyric. One famous example of a hidden message is on Frank Zappa's 1968 album, "We're Only In It For The Money." Annoyed by pressures from the album label, Zappa deleted a lyric, only to insert it in reverse on another track entitled "Hot Poop." Along with several expletives, the message, when played backwards, was a dressing-down of Zappa's critics. Other common features of hidden messages are ominous warnings, announcements of death, in-jokes about the band, and cryptic instructions.
Hidden messages are typically inserted via a technique known as backmasking, in which music or lyrics reverse to a message. An example of intentional backmasking is Jeff Lynne's instrumental track in the "Face The Music" album that intones, "The music is reversible, but time is not. Turn back! Turn back! Turn back!" Another type of hidden message is the subliminal integration of suggestions, such as the legal brouhaha that erupted over Judas Priest's 1978 album "Stained Class" which accusers said included the prompt "Do it! Do it!", inciting two fans to suicide. Eventually, the case was dismissed. Satanic hidden messages are another favorite. The Eagles song "Hotel California" came under the scrutiny of Fundamentalist Christian sects that asserted there was a hidden message saying, "Yeah, Satan organized his own religion."
While some groups assert that hidden messages in songs can affect people's behavior and actions, others argue that the power of subliminal messages is overrated. Subliminal messages may work as a boost to the subconscious, reinforcing something a person already wants, but the idea that hidden messages in songs can inspire people to act against reason, morals, and safety is far-fetched. Hypnosis is a good analogy to this situation. Hypnotists assert they can only hypnotize those who are willing to be hypnotized while those who are unwilling remain impervious to suggestion.
Hidden messages in songs can produce a hysteria that has nothing to do with religion, but rather to do with comedy. Weird Al Yankovic, the master of the song parody, released a single "Nature Trail to Hell" about a pretend slasher film. The song has lyrics, music, and content that alludes to Led Zeppelin as well as Michael Jackson, The Beatles, and Elton John. Most notably, at three minutes and 40 seconds into the track, there is deliberate backmasking. When played, the hidden message is "Satan eats Cheese Whiz."
Contrary to popular opinion, not all hidden messages in songs and backmasking are Satanic in nature. In fact, some hidden messages are positive or concerned. Such is the case with Franz Ferdinand who, on their 2004 single "Michael," inserted the message "She's worried about you, call your mother." Likewise, the band Tool tinkered with the track "Intension" by slipping in the backmasked message "Listen to your mother. Your father is right. Work hard. Stay in school."