album hired an outside engineer for the first time, bringing in Neil Kernon, who had previously worked with Kansas, Elton John and Peter Gabriel. Along with its usual hard rock fare, the band added tracks that featured a gospel choir and a bluesy sound, and Kernon's influence led to an album with a stronger emphasis on the band's rhythm section. Hartman also shifted his songwriting style, moving away from his practice of constructing albums around loose themes and writing tracks more personal in nature. The result was Unseen Power, a Petra album that, for the first time, was distributed by a secular record company, Epic. That, and the immensely favorable reaction to its release, led to talk of Petra following in the wake of Grant and Smith as a potential crossover hit, popular in both Christian and secular circles. "If it happens, then yes, we're ready", Schlitt said of the possibility. Though the secular breakthrough never came, the album was a hit, allowing Petra to top 6 million records sold since its inception – the most of any Christian artist at the time. The newly formed Hard Rock Cafe asked the band for materials to include in its restaurant displays, another first for a Christian band. And Petra became the only Christian band to play Farm Aid when it took the Texas Stadium stage before 40,000 people in 1992. Unseen Power opened No. 1 on Billboard's Christian music charts in November 1991 and stayed in the top 10 for seven months. Radio single "Hand on My Heart" was among the top 20 songs on Christian AC radio in 1992, and it was one of five tracks from the album to hit No. 1 on the Christian radio charts.Unseen Power garnered the band its second Grammy, again winning for Best Rock/Contemporary Gospel Album, and a Dove award, for Rock Recorded Song of the Year. Wake Up Call (1993) Taking what for its members was an unusual yearlong break between touring and recording the band's followup to Unseen Power, Petra emerged to a changing musical landscape requiring adjustment from the 20-year-old band. "I think we're on the verge of a new era for Petra", Hartman said shortly after the release of 1993's Wake-Up Call. "I'm not sure what that will be – but it won't be disco." As the broader musical climate soured on the arena-rock style that had been Petra's musical