ImageProgressive rock, the grandiose, often fussy pop subgenre known to its fans as "prog," more or less peaked in the 1970s, the decade of post-idealistic substance abuse and Laserium shows. Loved or loathed for instrumental flash, mad time-signature shifts, far-out lyrics and songs clocking in considerably past the 10-minute mark, the form ventured far afield from rock's visceral, earthbound origins. When the backlash came — in the form of punk and new wave — it was severe.

Yet the music never completely vanished. It was simply subsumed by new variations that continued to operate on the fringes, like "math rock" and neo-hippie jam-band noodling. That said, few of its latter-day practitioners have achieved the vaulting melodic glory of Yes or early Genesis, the brooding magnificence of Pink Floyd, the angular ingenuity of King Crimson or the glossy complexity of Rush.

I confess to having been ignorant of Chicago's Umphrey's McGee until now, though they've been making records and mounting wild improvisatory gigs for more than a decade. I should've been more attentive, and not just because their 1998 debut's title, Greatest Hits Vol. III, indicates that they share my sense of humor. The collective's new disc, Mantis, is arguably the first great prog album of the millennium.

It goes without saying that guitarist/singers Brendan Bayliss and Jake Cinniger, keyboardist/vocalist Joel Cummins, bassist Ryan Stasik, drummer/singer Kris Myers and percussionist Andy Farag are virtuoso players; they'd scarcely qualify for the genre otherwise. The guitar solos here alone are daredevilish enough to swell a prog fan's heart. But Umphrey's succeeds at this difficult game by focusing on songcraft. Like Yes in particular, but with a score of other thoughtful models, they devise singable tunes that shoot off in unexpected directions.

This is crazily original music, created in a pure spirit of adventure.
The dazzling title track, especially, showcases their ability to sustain the listener's attention for long stretches (in this case nearly 12 minutes). On "Cemetery Walk," a muscular funk groove blossoms into a gorgeous, heliotropic chorus; this is followed, most daringly, by "Cemetery Walk II," in which the song's themes are reiterated in electronic form (the often lazy purveyors of dance-floor electronica would do well to study UM's practically symphonic use of thematic variations in keeping the form interesting). "Turn & Run," meanwhile, melts a boogie feel into the weird-orchestra headiness of Hot Rats-era Zappa, with a momentary plateau in Yes-land circa Close to the Edge. In "1348" they merely deliver time-shifting riffage worthy of the Prog Hall of Fame.

Aside from the usual suspects, their influences seem to include the sinuous, world-grooving pop of the Police, the foxy jazz predations of Steely Dan, the high-lonesome dementia of the Meat Puppets, the synth-strewn bubblegum of Missing Persons, Phish's warped, sing-songy yarns, Primus' funk calculus, Metallica at its most pensive and about 50 other things. But Umphrey's doesn't just blend up a derivative smoothie from a couple of great record collections — this is crazily original music, created in a pure spirit of adventure that has largely expired in a time when most artists just dream of getting their three-chord number played over a "Grey's Anatomy" love scene.

Speaking of adventure, listeners who put Mantis in their computer disc drives can access a trove of online music, which I'm looking forward to checking out. I don't often say this, but I hope there are more 12-minute songs.