Rock en Espanol Double Bill Plays by the Rules

Wednesday’s double bill at the Key Club featuring Jumbo and Zurdok, two top rock en espanol bands from Monterrey, Mexico, proved the No. 1 rule of pop music appreciation: Never judge a band by albums alone. On record, Zurdok sounds superior, with sophisticated orchestrations and electronic effects that achieve uncanny echoes of the Beatles. Its rich and ambitious third album, “Maquillaje,” was a critical favorite last year.

But on stage Wednesday, Zurdok was a letdown. Stripped of its cellos, horns and studio tricks, the four-piece band sounded one-dimensional and mechanical. Chetes, its shy, mop-topped lead singer and keyboardist, seemed withdrawn and uninvolved, perhaps reflecting rumors of the band’s impending disintegration. The only spark during Zurdok’s droning, one-hour set came when Jumbo’s charismatic vocalist, Clemente Castillo, joined Chetes briefly on an acoustic number. Fans in the packed club cheered at the very sight of the lanky, leather-jacketed leader of Joom-boh, as they pronounce it.

During his band’s opening song, Castillo jumped around so spastically that his dark glasses flew off his head. It was a sign that the joint was about to start rocking for real. Although its studio work seems tame, Jumbo stirred up a midnight frenzy in the mosh pit during a surprisingly powerful set. At one point, Castillo stopped security guards from expelling an exuberant girl in hot pants and ponytails who had leaped up on stage, dancing like a delighted jumping jack.

“That’s what it’s all about,” he said in Spanish, arm around his rescued fan. “To be alive, to wake up and listen to rock ‘n’ roll!” Joined by members of Zurdok for an encore, Jumbo closed with a disjointed and unworthy version of “Sgt. Pepper’s Lonely Hearts Club Band.”

Pop music rule No. 2: Quit while you’re ahead.