It wasn’t exactly Jesus playing a guitar solo Friday night at the Riverside Theatre, but Dream Theater’s John Petrucci – whose long, curly brown locks and well-grown beard bear an odd resemblance to a certain Biblical figure – definitely fulfilled the role of savior for a small but rabid crowd of headbangers.

For almost two-and-a-half hours, the guitarist and his four disciples in Dream Theater stomped on the sorry state of modern mainstream metal with a precision performance of highly technical arrangements and operatic vocals. Consisting of only about a dozen long songs – including an encore of the 25-minute “A Change of Seasons” – the set played like a clinic for musicians in training, with each player receiving the opportunity to stretch out and display virtuosity. Any moshers who favor barked vocals, distorted guitars and fast-and-furious songs were wise to steer clear of this gig.

And while you can hear traces of Metallica, Alice in Chains and Soundgarden in Dream Theater’s progressive-metal music, those bands enjoy much greater success on rock radio. Dream Theater’s airplay – at least in Wisconsin – has been limited to a few tracks, none of which were performed Friday night.

On record, vocalist James LaBrie sings with an intensity virtually unmatched by his contemporaries. Live, that intensity increases and transmits to the audience, making it difficult not to strain with LaBrie as he reached for the high notes on 1992’s “Another Day” and “Home,” from the band’s latest album, Scenes From a Memory. LaBrie disappeared for extended periods during complex, multiple-passage jams by Petrucci, six-string bassist John Myung, sedate but brilliant keyboardist Jordan Rudess and Mike Portnoy (perhaps rock’s greatest drummer since Rush’s Neil Peart – no exaggeration). But whenever he took center stage, LaBrie’s extraordinary range, long hair and burning eyes set deep into his sockets lent a dignified aura of mystery and wonder to the proceedings.

Spock’s Beard, a California quintet that bridges the gap between old-school progressive rock (Genesis and Yes) and pop sensibilities (the Beatles and Cheap Trick) opened the evening with a rousing five-song, 50-minute set of headlining caliber. Front man Neal Morse goofed with his guitar-playing brother, Alan, who mimicked faux rock-guitar antics, and he joined Nick D’Virgilio for a two-man drum session.

Unfortunately, an earlier-than-posted start time meant many fans were still filing into the theater as Spock’s Beard played. Still, the fact that such a zealous albeit slight crowd gave almost four hours of its time to these two outstandingly unconventional bands on a magical Friday evening (during the waning days of summer, no less) is enough to restore one’s faith in the redeeming power of music.

---Michael Popke