Backmasking is a technique in which audio is recorded backwards and then played forwards to create hidden messages or sounds. In "Stairway to Heaven," it is believed that the lyrics and music contain hidden references to Satan when played backwards.
While there are several theories and interpretations of the lyrics and music when played backwards, there is no solid evidence that Led Zeppelin intentionally included backmasked messages in the song. In fact, the band has denied any intentional use of backmasking in their music.
One example is in the line "If there's a bustle in your hedgerow, don't be alarmed now" which, when played backwards, is believed to sound like "Here's to my sweet Satan." Another example is in the line "And she's buying a stairway to heaven" which, when played backwards, is believed to sound like "There's no escaping it." However, these interpretations are subjective and may not be intentional on the part of the band.
There have been numerous claims of backmasking in songs by Led Zeppelin, as well as other artists such as The Beatles and Pink Floyd. However, these claims are often based on subjective interpretations and have not been confirmed by the artists themselves.
The controversy surrounding backmasking in "Stairway to Heaven" stems from the fear that these hidden messages may have a negative influence on listeners, particularly young and impressionable individuals. There have been debates over whether or not backmasking can actually be perceived and understood by the human brain, and whether or not it is a deliberate attempt to promote satanic messages.