Petra is an American music group regarded as a pioneer of the Christian rock and contemporary Christian music genres and was, for many years, regarded as the "world's most popular Christian rock band. Formed in 1972, the band took its name from the Greek word for "rock". Members Bob Hartman -Guitar, backing vocals John Lawry -Keyboards, keytar, backing vocals John Schlitt -Vocals Greg Bailey -Bass, cello, backing vocals Cristian Borneo -Drums