Correction: An earlier version of this review incorrectly identified which member of Alt-J said goodbye at the end of the set and then announced that the band would be back in Washington in September. It was keyboardist Gus Unger-Hamilton, not guitarist Gwil Sainsbury. This version has been corrected.

Alt-J performs a Monday concert at the 9:30 Club. (Kyle Gustafson/For The Washington Post)

The band doesn’t favor noise when on a stage or in a studio, but there’s a real loud buzz about Alt-J. After releasing just one full-length album, last year’s “An Awesome Wave,” the British quartet is selling out major rock venues, including the 9:30 Club on Monday, where Alt-J quietly justified the hype.

A stand-up club packed to its rafters isn’t a perfect setting to be introduced to Alt-J, whose members were all mates at Leeds University before plugging in together and naming themselves after a Mac computer command. The set, which with minor exceptions mirrored the track listing on “Wave,” was full of repeated electric keyboard and quiet, melodic guitar riffs but nary a power chord. The typical tune had passages made up of the sort of ambient music that can get you all Zen when you’re sitting on a couch or in a driver’s seat on a long road trip.

But Alt-J kept its songs in the sub-four-minute range, leaving no time for shoegazing.

And lead vocalist Joe Newman’s delivery was never less than fascinating. Newman occasionally syncopated his delivery and frequently gibberized his English, making for a compelling combination of Dave Matthews and Nina Simone. It wasn’t easy to tell exactly what words he was singing on “Buffalo,” a song from the “Silver Linings Playbook” soundtrack and one of the night’s rare non-LP offerings, but that seemed by design. The performance again proved that unintelligibility isn’t necessarily a negative in pop music (think early Michael Stipe vs. late Michael Stipe). Newman’s failure to enunciate made the performance only more mesmerizing.

“Dissolve Me” came off as melancholy psychedelia, with mournful group harmonies of the sort the Beach Boys might have favored if they’d grown up in a foggy clime instead of sunny Southern California. “Fitzpleasure” and “Matilda” had trebly guitars and tribal-sounding rhythms, a mix not too distant from the juju music Nigerian star King Sunny Ade introduced to Western pop in the early 1980s.

Alt-J’s songs aren’t the only things that are notably short. A curse of being a new buzz band is a shallow pool of material. And the band has chosen not to pad its set list with covers or unreleased material. So lots of folks looked at their watches or cellphone clocks and giggled in disbelief when keyboardist Gus Unger-Hamilton said goodbye and led the lads offstage after just 45 minutes, a remarkably brief set for a headliner.

Alt-J returned for a quickie encore after only 30 seconds in the wings, and just before calling it a night got a great roar from the fans when Unger-Hamilton announced that the band would be back in town in September. New to show-biz or not, Alt-J already knows how to leave ’em wanting more.

McKenna is a freelance writer.