Robyn at Pitchfork Music Festival (Photo by Kate Gardiner/NewsHour)

The first serious signs of life on day one of Pitchfork 2010 came courtesy of the 31-year-old native of Stockholm, Sweden, Robin Miriam Carlsson, better known simply as the dance-pop artist Robyn.

Bounding about onstage as if she was leading an aerobics class, Robyn’s defiantly retro, synth-laden grooves and chant-along choruses were nothing new: Think of Cyndi Lauper fronting an amalgam of every ridiculously coiffed English pop band in heavy rotation on MTV circa 1984. But the sheer exuberance of it all was invigorating and undeniable, and the sun-baked crowd came to life as the unassuming Everywoman led them through a high-octane workout.

Lollapalooza can have Lady Gaga. Robyn owned day one of Pitchfork.

Broken Social Scene (Photo by Kate Gardiner/NewsHour)

As the penultimate act of the day on the main stages, the Canadian orchestral/power-pop supergroup Broken Social Scene suffered slightly from the same problem evidenced on its last album “Forgiveness Rock Record”: A weakness in the songwriting that doesn’t always justify the grandiosity of its arrangements. But the sound of the band was bigger than ever at Pitchfork as John McEntire of Tortoise and Soma Studios added second drums and the group brought out horn and string sections that included local hero Paul Mertens and and heroine Susan Voelz, and the lushness of the sound coinciding with the setting of the sun and the first kind, cool whispers of a breeze made for some magical moments.

Finally, Modest Mouse closed things out with a set that was… perfectly okay.

Modest Mouse (Photo by Kate Gardiner/NewsHour)

The long-running Washington state art-pop band seemed like an all-too-predictable booking for Pitchfork: Since the release of its last album, “We Were Dead Before the Ship Even Sank” (2007), the group has to have played Chicago at least half a dozen times, and some of those with Johnny Marr. Even with the Smiths legend on guitar, the group has never been an exceptional live act: On really good nights, its skewed rhythms and off-kilter hooks can make your head spin, but there aren’t a lot of those, and this wasn’t one of them. Aside from the one truly inspired tune of the night, a version of “Dramamine” from the band’s first album, the set was an underwhelming way to end the day.

With the strongest overall bill on Sunday, and the most anticipated single set of the fest on Saturday night with LCD Soundsystem, the story of Pitchfork 2010 may just be one of a slow but steady build.