The history of the blues is complex, meandering its way from rhythmic African chants to Southern spirituals to Chicago pop hits. In Portland Center Stage's final production of the season, however, this history gets only shallow treatment. That's a shame. The show is a rousing, entertaining jaunt, but for those unschooled in the development of the genre, more guidance would have been helpful.

The more than 30 musical numbers in It Ain't Nothin' but the Blues unfold chronologically. The first act features the seven-member cast in Depression-style garb, relying on acoustic guitar and simple percussion to perform the plantation work songs and church anthems. Act two adds a five-piece band and spangled evening wear, placing us in a Chicago nightclub. The performers, largely out-of-towners, are terrific and varied: Mississippi Charles Bevel shows phenomenal range and soulful restraint; Jennifer Leigh Warren has powerhouse pipes and endearing spunk; and "Sugaray" Rayford is built like a linebacker but whips out some of the show's smoothest dance moves. Director Randal Myler, one of five creators of the show, keeps the staging simple and the choreography subtle. 

In Ken Burns style, historic photos spool across two giant screens behind the performers. Though often poignant, these images are presented without context, doing little to flesh out the narrative. More satisfying are the bits of banter, which allow for frisky interaction among the cast. The playfulness continues through the songs, particularly during some of the raunchier numbers; Chic Street Man milks "Crawlin' King Snake" to squirmy, hilarious effect. The performers encourage audience participation, so here's a warning: Be prepared for some call-and-response, though a few claps and snaps will do just fine.

As a musical revue, It Ain't Nothin' is delightful. It's got mournful solo pieces and high-voltage ensemble numbers, and minimal dialogue means the pace rarely slows. But as a piece of theater, it lacks something. The title describes the show literally; I wanted a little more.

SEE IT: It Ain't Nothin' but the Blues is at the Gerding Theater, 128 NW 11th Ave., 445-3700. 7:30 pm Tuesdays-Fridays; 2 and 7:30 pm Saturdays-Sundays. Through June 24. $39-$69.