MANSFIELD, Mass. — With the addition of former Smiths guitarist Johnny Marr, Modest Mouse, who headlined a rock-laden Download Festival last night at the Tweeter Center, picked up some rock muscle for their wide palette that can include flute, trumpet, accordion, melodica, and bowed upright basses. There was real power to live renditions of the openers “Invisible” (from their latest album, We Were Dead Before the Ship Even Sank) and “Paper Thin Walls.”

But they’re still Modest Mouse, and that’s an acquired taste. Their songs basically run the emotional gamut from nervous to, um, edgy, with Isaac Brock channeling his inner Black Francis, going on nearly psychotically about what usually turns out to be not much, even on the relatively upbeat “Float On,” even occasionally throwing in a plinky banjo to sound even more uptight.

Still, Marr lent a masterful touch, particularly his cutting fills on “Education” and bubbly tremolo on “Missed the Boat.”

Guster, preceding Modest Mouse, stumbled out of the blocks, playing several wan pop songs with thin-sounding guitars, such as the openers “One Man Wrecking Machine” and “The Captain.” Even then, their opaque vocal harmonies and loping dance groove usually carried them through, and later on they opened up their toolbox. Drummer Brian Rosenworcel shifted between his usual complex hand-percussion kit and a regular drum set (and on several songs an auxiliary drummer helped out), singers Ryan Miller and Adam Gardner passed around guitars and basses, and Miller and bassist Joe Pisapia took several turns at the keyboard. The sprawling “Come Downstairs and Say Hello” started with a hushed vocal-guitar interlude, went through a danceable, two-chord middle section with chilly synthesizers and ended with a trumpet solo from Gardner.

Neko Case opened the mainstage with her force-of-nature voice, which has a clear, uncolored power. Her songs are mostly a sort of country-indie hybrid that appeals to people who don’t like to say they like country music. There were plenty of languid ballads, some of which, such as “I Wish I Was the Moon,” had hooks that stuck deeper than others.

Karen O led the Yeah Yeah Yeahs, in a black-and-white cape with tons of tinsel, led the New York trio (with an auxiliary bassist/keyboardist/guitarist) through the sunset hour with an impressive variety of singing, screaming, cooing and whispering, all the while jumping, stretching, praying and whirling, with a take-no-prisoners attitude and a demented stage presence leavened by seemingly incongruous smiles.

Guitarist Nicholas Zinner put harsh, evil distortion on his guitar and drummer Brian Chase pounded out simplistic rhythms with heavy four-on-the-floor bass drum. The effect was abrasive and purposely ugly, and also set up the relatively poppy, Siouxsie Sioux-like “Cheated Hearts” and the two lovely closers, the hit “Maps” and “Turn Into.”

Wolf Parade headed an afternoon second-stage bill with their own brand of hi-drama rock, with a mix of yelping vocals and squalling keyboards that occasionally echoed Bauhaus and Television.

rmassimo@projo.com