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.