It's a full 10 years since the Allman Brothers pioneered their new style of Southern rock 'n' roll. Last night at the Merriweather Post Pavillion two descendants of the Allmans took that style in opposite directions. The opening act, Sea Level, advanced the style into true improvisation. The Atlanta Rhythm Section tamed the style with polished pop arrangements.

Sea Level's set exceeded anything they'd done on earlier records or tours. Their closing instrumental was truly impressive electric jazz. Ex-Allman brother Chuck Leavell led the way with an unusually moody synthesizer and cascading piano solos. Guitarists Jimmy Nalls and Davis Causey upped the tension with alternating blues phrases. Ex-Allmans bassist Lamar Williams and ex-Wings drummer Joe English broke up the rhythm with their own accent. Randall Bramblett closed with a squawking alto sax solo.

The band proved its versatility by encoring with a rousing rhythm 'n blues number. Nalls and Causey dueled on slide guitar; Leavell and Bramblett raced each other on boogie-woogie piano.

The Atlanta Rhythm Section, by contrast, stuck close to their arrangements made familiar on the radio. Even when they took solos on their hits like "Imaginary Lover" and "I'm So Into You," they never ventured far from the song's basic riffs. The band's biggest talent is in fashioning catchy hooks and playing them tastefully. Their live show added little to the records.