Scarfolk's first music festival in 1973 was only given the go ahead with the stipulation that all bands play songs which contain backmasked content. Additionally, they had to perform the songs backwards so that the subliminal messages could clearly be heard and understood by the audience.
Infamously, local prog-group Beige's* performance of their 3-hour epic song-cycle about a school gym teacher with missing-personality disorder contained subliminal elements that triggered mass hysteria. Many audience members hallucinated seeing in the sky the shape of satan with a trident, though others argued that it looked more like an intercontinental travel plug.
*For more information about Beige go here.
