While almost everyone is in agreement that day three is the strongest of Pitchfork 2010, it started out on the main stages with only slightly more energy than the past two days.

To be clear, I have nothing against chill-out music as a genre; I just expect ambient pop to measure up to the best of what I’ve heard from that sound in the past, whether it’s the godfather himself, Brian Eno, or Aphex Twin in his ambient mode, or the mellower of the early ’90s shoegazers. Too much chillwave, doesn’t rise to those peaks on record. And even if it did, that’s not guarantee that it can carry a crowd of 18,000 in the festival setting. Especially when it’s interspersed with just plain generically jangly indie rock.

Kicking things off on Sunday, not long after a heavy rain yielded to plain old oppressive heat and humidity, Chicago’s Allá gave the crowd a taste of chill sounds at their best, with singer Lupe Martinez cooing seductively as the musical team of brothers Jorge and Angel Ledezma created lush pillows of sound and gently percolating, occasionally Latin-flavored grooves behind her.

At his mellowest, California-bred singer-songwriter Cass McCombs brings to mind a less polished Lloyd Cole; at his best, which is very good indeed, things tip more toward garage rock and Paul Westerberg. During the second main-stage set of the day, McCombs gave a taste of both, drawing from his fourth album “Catacombs” (2009), as well as dipping deeper into his back catalog for a strong if never really fiery set.

Girls, unfortunately, were another step back toward mid-tempo mediocrity. The twee, tinkley sounds seem so fragile that merely listening too hard might cause them to fall apart—though the precious mix of the floweriest San Francisco circa ’67s psychedelia and mellowest Smiths isn’t helped by the lack of charisma evinced by bandleaders Christopher Owens and J.R. White. Gotta say, I would have loved to have heard another set from Allá instead.