There is more than one artist with this name: 1) Petra is a Christian Rock band formed in 1972 by Bob Hartman, Bill Glover, John DeGroff, and Greg Hough. "Petra" means "rock" in NT Greek, making the band name a triple pun. Rising from the Jesus music movement, and initially signed to [recordlabel]Myrrh Records[/recordlabel], they fought to gain acceptance and recognition in a church culture that at the time believed rock music to be off-limits. Over time they eventually won over most of their critics