The heat showed no signs of breaking at Austin's Zilker Park yesterday (Sep. 15), as the Arcade Fire, Clap Your Hands Say Yeah and Arctic Monkeys churned out fiery sets to massive crowds at the sixth

The heat showed no signs of breaking at Austin's Zilker Park yesterday (Sep. 15), as the Arcade Fire, Clap Your Hands Say Yeah and Arctic Monkeys churned out fiery sets to massive crowds at the sixth Austin City Limits festival.

Although noticeably muddied sound seems to follow each band on the AMD stage, the Arcade Fire brushed it off by turning in memorable versions of songs like "Keep the Car Running," with Win Butler commanding the crowd with the tune's signature mandolin. "Antichrist Television Blues" and "Neighborhood #3 (Power Out)" were also vivacious crowd pleasers.

In a set just beforehand, the Arctic Monkeys didn't suffer quite the same sound issues. The U.K. band tore through hit after hit, with fans mostly eating up the material from the Monkeys' debut, "Whatever People Say I Am, That's What I'm Not." Highlights included a raucous version of "The View From the Afternoon," "I Bet You Look Good on the Dancefloor" and the ska-tinged "A Certain Romance."

Over on the AT&T Blue Room stage, the sound was much better, and Brooklyn's Clap Your Hands Say Yeah took full advantage. Alec Ounsworth's nasal voice could be heard clearly and loudly on cuts like the funky "Satan Said Dance," the spaced-out "Skin of My Yellow Country Teeth" and "Details of the War."

Alt-country fans were treated two stellar performances earlier in the day from Austin's own Kelly Willis and troubadour Steve Earle. Willis' set was one of tender, sweet country ballads from her extensive catalog. But she didn't relegate the performance to just downtrodden fodder, as "Nobody Wants To Go to the Moon Anymore" and "Not Forgotten You" gave the crowd reasons to get out of their lawn chairs.

Midway through his set, Earle was joined by his wife Allison Moorer on the New York City ode "Down Here Below," one of several tunes from his about-to-be-released "Washington Square Serenade." Most of the performance was solo, but Earle also employed a DJ to scratch and provide beats during "Ocycotin Blues," "Satellite Radio" and the Tom Waits cover "Way Down in the Hole."

Austin City Limits wraps today with performances from Bob Dylan, Wilco, My Morning Jacket and Bloc Party. For additional coverage, visit the Billboard blog at JadedInsider.com.

Questions? Comments? Let us know: @billboard

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