Something bizarre has happened to Modest Mouse [ tickets ] since the release of their most recent album, "Good News for People Who Love Bad News." Or, actually, something has happened to their fans.

Because of the popularity of their catchiest song to date, "Float On"--now a staple on VH1 countdowns and Top 40 radio--Modest Mouse, which so recently attracted alt-rock lovers with their unique pop-synth style and lead singer Isaac Brock's alternately whimsical and stormy personality, is now a favorite of teeny-boppers and even 10-year-olds, who, along with their parents, made up a good part of the sold-out crowd at the band's show on Monday (7/19) night. We're talking a crowd so young that when someone yelled out "Freebird," people thought it was creative and funny.

It's a strange combination. While "Float On" is a bright blast of driving music that could get anyone on their feet, the majority of the band's songs are on the darker side--layering bitterness, anger and some twinges of hope with complex melodies the band has made completely their own. In any given tune, Brock can go from mellow thoughtfulness to seething rage in seconds. In "Black Cadillacs," a new song that had everyone--even the kiddies--singing along, he calmly offers the words, "And we were laughing at the stars/While our feet clung tight to the ground," to follow, screaming, with "But we were all still just dumb, dumb, dumber than the dirt, dirt, dirt on the ground." (And this is the FCC-friendly part of the song.)

Still, during a performance that lasted just over an hour, the band put together an impressive set of music--mostly from the new album--that demonstrates how very far they've come. With two amazingly syncopated drummers, a narrow electric cello, multiple guitars and keyboards, Eric Judy's incredible bass-work, Brock's banjo (that incited immediate cheers), and his tripped-up double mic, the band worked powerfully together with barely a look between them.

Moving from chunky acoustic clap-alongs ("The Good Times are Killing Me"), to the peaceful "The World at Large" and disco-y "The View," the band also revisited older songs--notably "3rd Planet" and "Paper Thin Walls" from "The Moon & Antarctica," and the pre-encore "Doin' the Cockroach," that had Brock face-first into his guitar, moaning words through the pick-ups.

The band played "Float On" early, and while it was a rollicking, freshly revised version, it also seemed a sign that the musicians wanted to get the single over with to get to what they're really made of. In turns melancholy and actually frightening (Brock, in "Satin in a Coffin," screeching "Are you dead or are you sleeping/God I sure hope you are dead"), they proved that, despite what their fan-base may currently look like, this is, in every possible way, music for grown-ups.