Unannounced shows at SXSW are the quintessential marketing tactic. They exist to give festival showcases an air of speculative mystery, but they must play their hand far enough in advance for #brand influencers to show up, lest civilians take all the available spots. These secret shows can end up being uninteresting (Neon Indian DJ set, anyone?), but many of the rarest and best one-offs hide behind a veil, so asking around and constant Twitter scouring is required.

Early on Friday in Texas, I got a tip that Durham’s Sylvan Esso would play the unannounced closing set Friday night at Mohawk. A headlining slot on the second-largest night of SXSW? At one of the most trafficked Red River venues? I had known that Nick Sanborn was in town doing a few sets as his solo project, Made of Oak, but this notoriety came as something of a surprise. To wit, I had just seen Erykah Badu play the exact same one a.m. slot at the same venue two days prior.

Word got out quickly, as the long was line. A bit of this could be attributed to Merge’s beloved Wye Oak, who played immediately before Sylvan Esso. I got in just in time for the duo’s last two songs, as heartbreaking as ever.

When Sylvan Esso arrived onstage, they proved much braver band than anyone gives them credit for. Instead of opening with trusted crowd-pleasing hits like “Play It Right,” they waved to the crowd and launched into a run of unknown songs, which singer Amelia Meath later revealed they had never done live before. I could see why they took this gamble: These new songs sound larger than anything they’ve done to date. The BPMs are higher, almost suggesting drum and bass. The hooks are massive. The crowd went for it.

I’ve seen Sylvan Esso at least five times in various places, and this was easily the best crowd I’ve ever seen them play to, which also came as a surprise. Given the warm, drunk reception that SXSW crowds at larger venues tend to give, I expected a raucous time, not the level of fandom the crowd showed. Most of the audience knew all the words to their singles. When “Hey Mami” arrived, Meath turned the mic to the audience, who bellowed every line back. Sylvan Esso hasn’t exactly been the local band playing your friend’s backyard for a while now, but as a Triangle band representing nationally in a big way, it was a sight to see.