By Allen Howie

It's April 14, the tax return's finished, the weekend's just around the corner, the mercury's at 80 degrees, NRBQ has rolled into town and all's right with the world. With two members of the late Sun Ra's Arkestra in tow, the show promised to be loads of fun.

As our waitress at Jim Porter's demurely observed, "They're so ... sloppy." And for NRBQ fans, that's half the attraction, that dangerously loose approach that means anything can happen — and probably will. These guys were grungy before it was hip, groovy long after everyone else had given up, and cool through it all.

They ignited their show at Jim Porter's with the manic spelling lesson of "Spampinato," giving Sun Ra veterans Tyrone Hill and Dave Gordon the chance to serve up some Memphis soul, then slide into some funky Dixieland. Soon, solos were ricocheting around the room at an alarming rate.

Listening to NRBQ is like cramming four decades of rock and roll into an hour. The band will start with the riff from a million '50s ballads, strip the sucker down to the chassis, then put the pedal to the floor. The very next number, they're giving the Dave Clark Five reconstructive surgery, or burning pop and classical melody lines into a molten blues groove. Weirdly angelic Everly Brothers harmonies waft over the greasy grind, a big, fat trombone solo walks in and plops itself down, and everyone embarks for a quick tour of Sun Ra-style avant-pop.

"Wild Weekend" was the musical equivalent of nuclear fission, with less toxic waste. "Girl Scout Cookies" showed up from the band's new album, Message for the Mess Age, replaced a song or two later by the jangly beauty of "If I Don't Have You."

Like a steam engine roaring out of control, the band tore into "Rocket in My Pocket," gave a fair approximation of Bill Haley on steroids, and, during the first of two encores, bit down hard on Johnny Cash's "Get Rhythm." They started their second encore over a tribal beat, with a tune whose lyrics consisted mainly of, "Here comes Joey/Here comes John," split in two by a huge trombone solo and an equally monstrous trumpet excursion. By the time they rolled up their tent near 11:30, NRBQ had tracked mud all over the nice, clean kitchen floor of popular music, then invited everyone else to slide around for awhile.