Only Knows ("[Back To] The Rock"), as well as re-recordings of hits from that era. The band released a companion live CD and DVD in 2011. Musical style Petra's style changed significantly over the decades in an effort to remain relevant to the youth it was trying to reach but remained within the rock genre implied by its name. At its inception, the band's style was eclectic, borrowing from musical influences as diverse as The Eagles, Lynyrd Skynyrd and Kansas. Early albums featured electric double-guitar leads reminiscent of the Allman Brothers Band. In the 1980s, the band began using keyboards and synthesizers to complement its guitar-based rock. Early in the decade, Petra produced a straightforward pop/rock sound reminiscent of Foreigner, while increasingly using synthesizers and electronic effects as the decade progressed. By the late 1980s, Petra used a change in vocalists to embrace a guitar-based hard rock style similar to Def Leppard, Aerosmith and Journey – a style that, along with the growing popularity of Christian rock as a whole, led to Petra's peak success. With the rise of alternative rock in the mid-1990s, the band's albums subsequently featured an increasing reliance on acoustic guitars and mellower tunes, including a fully acoustic album. Petra returned to its roots with a hard rock album in 2003, while the 2010 Classic Petra reunion was billed as an effort to re-record some of the band's early 1980s hits "with a modern edge". It included two new songs that fit within the guitar- and keyboard-based rock style that marked much of the band's early career. History 1972–1979: Inception In the early 1970s, songwriter and guitarist Bob Hartman met bassist John DeGroff and formed the band Dove, which he quickly disbanded when DeGroff left to attend a Bible school in Fort Wayne, Indiana, known as the Christian Training Center. Hartman soon followed, and in 1972 he and DeGroff joined two classmates, guitarist Greg Hough and drummer Bill Glover, to form Petra. The band played small Midwest venues such as churches, coffeehouses and parks, to share the message of Christianity with concertgoers. Glover said on an interview "we weren't picky and we wanted to get God's Word out to our peers. We would set up in parking lots, parks, college campuses, coffee houses, etc." A frequent venue was a Fort Wayne Christian-themed coffeehouse named The Adam's Apple. This mix of evangelism with rock placed Petra among