The Boulevard Pool morphed into a miniature music festival last Thursday, as sun-soaked fans packed in for X107.5-FM’s Our Big Concert, featuring headliners Capital Cities and Phantogram, plus six up-and-coming bands.

I arrived around 7:30 p.m. for Illinois garage-rockers The Orwells. Singer Mario Cuomo’s maniacal stares and awkwardly sexual gyrations failed to get the crowd going, and while performances of rising radio hit “Who Needs You” and a cover of The Foundations’ “Build Me Up Buttercup” perked things up momentarily, the set still felt awkward.

At 9:30, South African rock band Kongos took the stage with an odd blend of accordion-fueled funk-rock (you read that correctly). Known for the recent hit “Come With Me Now,” the four brothers—all sons of ’70s singer John Kongos—played a handful of original pop-rock cuts and jam-rock-inspired songs before inviting rapper Mozart onstage for a bizarre hip-hop infused cover of The Beatles’ “Come Together.”

Patience paid off when electro-pop duo Phantogram took to the stage for a first-ever Las Vegas appearance. The group’s bass-driven synth-pop and Sarah Barthel’s whimsical, airy vocals floated above the Strip as glowing lights flickered to each pulsating beat. Breakout hit “Mouthful of Diamonds” felt especially vibrant and clean.

By the time Capital Cities took the stage, nearly half the crowd had cleared out, probably because the LA band has performed here several times recently. This time, the duo’s set was enhanced by a wonderfully skilled trumpeter and a couple of cheesy-but-cute choreographed dance moves. For fans of acts like Chromeo, Capital Cities is a must-see.