Tetragrammaton Records was an American record label founded in the late 1960s by artist entertainment manager Roy Silver, Bruce Post Campbell, Marvin Deane, and comedian Bill Cosby (whose manager was Roy Silver). The term "Tetragrammaton" refers to the unspeakable Hebrew name of God.Tetragrammaton's most successful act was the first incarnation of the rock band Deep Purple. The label was also responsible for issuing John Lennon and Yoko Ono's 1968 Apple Records album, Unfinished Music No.