Playing to a sold-out crowd at the Civic Theatre, the art-rock band from Leeds talked about sex but couldn't live up to its thematic ambitions.

Amid thick smoke and red laser lights stood four men dressed in black button-downs, dour looks on their faces. A sold-out crowd at the Civic Theatre screamed the lyrics to "The Gospel of John Hurt," a song about Ridley Scott's 1979 film Alien, but the members of alt-J refused to give an inch, to let their bodies contort with the rumbling bass. They stoically sang the letters "E-X-T-I-N-C-T" and talked about civilians in space. The person next to me danced ecstatically.

It's still strange to see alt-J's cerebral folk-and-electronic-inspired rock music heralded as pop. Some might criticize the band for overcomplicated, fussy compositions but its greatest strength has always been restraint. The band's geometry metaphors, abundant pop culture references, and dense sound--deemed calculated, messy or strange by some critics--are all just distractions from what the band is ultimately concerned with: sex.  And on Monday night, alt-J won over the crowd by not showing all its cards.

Alt-J has solidified its live performance in the past few years. The band's pulsating music translated well to the stage, where the quiet, kind ballad "Warm Foothills" was fleshed out, which made up for the absence of the recording's guest vocals (Connor Oberst, Marika Hackman, Lianne La Havas, and Sivu). A booming version of "Breezeblocks" was also of particular note. Underneath everything was a palpable tension that propelled the dramatic set.

Behind stuttering drum lines, droning lyrics, and atmospheric guitar, alt-J holds something out of its audience's reach. The band's ability to withhold so much is due not only to the sheer amount of sound heaped over everything, but also to the members' general anonymity and stoicism onstage (the quartet barely moved their feet). Alt-J isn't trying to bowl over its audience with personality or gregarious stage banter, which works in its favor. The band did, however, make some attempts to engage the audience. Lead singer Joe Newman encouraged fans to sing along on multiple occasions, and a band member threw a merch T-shirt into the crowd as if it were a baseball game.

Ultimately, the set was a performance of foreplay. The tonal restraint was a smart move, especially when its lyrics are as upfront as those on "Fitzpleasure" ("In your snatch fits pleasure / broom-shaped pleasure"). The band cultivates a sense of mystery and restraint, nudging its fans to put more effort forth. It withheld sexual tension and helped the set maintain its energy.

About a third of Monday's setlist was from this year's release This is All Yours. While the band's debut album An Awesome Wave dealt with sex in pretty straightforward fashion--namely, that sex happens--its newer material attempts to stretch that theme. The band opened with single "Hunger of the Pine," which features a sample of Miley Cyrus' song "4x4." Cyrus' disembodied voice declared, "I'm a female rebel," and floated in and out of the song. It's a strange gamble that paid off sonically but made no sense thematically. It was a fine, fun work of pastiche but a lukewarm attempt to speak about feminism and female power. Its other lyrics made no other remarks on the subject and the gesture ended where Cyrus began. A sample does not a statement make. 

Alt-J encored with "Nara", a song they have stated is about homosexuality, though the lyrics don't really stretch much further than saying that homosexuality exists. Their attempts to express more were bland, especially when the gesture came from stern men clothed in all-black, backlit by strong, red strobe lights while bass rumbled. Alt-J wants to be more ambitious in its sexual themes, but it does so while reiterating machismo in its presentation.

Sometimes though, playing it safe was itself a form of experimentation. The band has mentioned that its lead single "Left Hand Free" was an effort to appease its US label, for which they quickly crafted the least alt-J song ever out of a joke riff and defiantly clichéd drumbeat. Of course, the label loved it. There was no trace of irony when they played the song Monday and, per usual, the band barely cracked a smile. The crowd danced easily to the catchy song. What here was a joke to alt-J, and what was serious? Sure the music is fun, but sometimes it stops being so when it feels the joke might be on you.