Riding high on the success of their excellent third album, “I See You,” British dream pop band, the XX is one of the top billed artists at the 2017 Austin City Limits Festival. The band appears seventh on the roster, immediately after the six artists who will presumably play the headline slots on the big stages each night. Most likely, that sets them up for a 7 p.m. sunset performance on one of the larger side stages.

Suzanne Cordeiro/For American-Statesman

At first glance, the XX seems like a somewhat odd choice for a massive festival act. They make intricate songs that delve into the complexities of relationships. As they parse the varying shades of love and loss, vocalist Romy Madley Croft tends to be understated. Hair falling across her face, she often whisper sings. So how will this play to a crowd of thousands in Zilker Park?

» A-List Photos: The XX at ACL Live

In the first of two sold out nights at ACL Live Wednesday, they delivered an exhilarating performance that indicates it will be simply sublime. Here are five reasons why:

1. They are masters of big emotional swells that will put you in your feelings. With giant floor-to-ceiling mirrors revolving on all corners of the stage, reflecting flashing lights and creating a haunted fun-house effect, the trio opened with the smash single “Say Something Loving,” a song about conquering insecurities to open yourself to the possibility of love. It’s a song that ebbs and flows, winding its way into the glorious cascade of the emotional chorus. It washed over the ACL Live crowd, a good portion of whom were couples on date nights, with buoyant brilliance. It was easy to picture a mass of thousands at Zilker Park swaying together in the golden light while colorful beach balls bounce over the crowd.

2. They’re not guitar rockers, but Croft’s guitar work drives the band. They employ ample strobes and startling bursts of light, but the XX isn’t an intrinsically flashy band, driven by larger than life personalities. They don’t spend a lot of time on stage banter, instead allowing the music to speak for itself. Croft uses languid guitar lines to build moody grooves and, at times, seems most comfortable on stage vibing with bassist Oliver Sim during the instrumental breaks. They face each other and feed off the energy of their individual sounds locking together and playing off each other. They’re an act that takes their musicianship very seriously.

3. Jamie XX on the beats. Standing behind an elaborate control panel of samplers, keyboards and drum pads that would not look at all out of place in Bruce Wayne’s basement, the rhythm king is the XX’s secret sauce. The impeccable instincts that inspire him to lay a house beat under the flowing melody on “On Hold” or to unleash the pulsing rhythm on the vaguely sinister “Dangerous,” allow the XX to straddle the line between EDM and melodic dream pop in a very modern way that’s perfectly suited to the new face of ACL Fest.

Suzanne Cordeiro/For the American-Statesman

4. Their catalog is well-stocked with earworm singalongs. From the lilting melody of “I Dare You” to the stutter stop emotion of “On Hold” or the plaintive chorus of “Say Something Loving,” the band excels at distilling complicated, but relatable feelings into simple melodic phrases that are easy to sing. A crowd of a couple thousand beautifully amplified all of these songs at ACL Live and at least five times that joining in on the Great Lawn at Zilker will be a soul-stirring experience.   

5. The love is there and it feels very real. No one is exactly sure how the XX became one of the biggest bands in America, including, it seems, the band themselves. They were greeted ecstatically with long, extended cheers at the top and bottom of the set and multiple times throughout. They recorded part of the new album at the Marfa Recording Company and seemed very genuinely happy to be back in our state. As the band prepared to leave the stage, Croft was moved almost to tears, as she tried to respond to the warmth from the crowd. “We don’t expect it and it means a lot to us. We do appreciate each and every one of you,” she said. And the love flowed freely once more.