IT'S A SAD fact of life that what you see in concert isn't always what you get on record. Studio sessions impose certain restraints and commercial realities on bands, making them sound far more reserved than they do on stage.

Take the new album by Louisiana accordionist Wayne Toups. In concert, Toups can be magnetic. For all the dance appeal of Cajun and zydeco music, there are few band leaders that possess Toups' unbridled energy and showmanship. He's young, charismatic and has a powerful voice, easily strong enough to be heard over the infectious rhythms his band hammers out. There's more than a hint of all of this on his new album "ZyDeCAJUN" (that's also the name of his talented band), but the music never packs the same wallop.

For one thing, the addition of pedal steel guitar on tunes like "My Friend" and "Belizaire Waltz" give the album a lilting country flavor, not an unpleasant sound but nowhere near as compelling as the accordion-driven dance tunes on the album. It's only when the band rips into songs like "Zydeco Baby" and "Going Back to Big Mamou" that its real strength and promise come into focus.

The Sun Rhythm Section's album "Old Time Rock & Roll" suffers from a similar fate. It never quite lives up to this all-star rockabilly band's stage show, though it does manage to come close at times. The lineup of Memphis legends speaks for itself: D.J. Fontana and J.M. Van Eaton on drums, Sonny Burgess and Paul Burlison on lead guitars, Stan Kessler on electric bass, Marcus Van Story on rhythm guitar (and slap bass) and Smoochy Smith on piano.

Sharing the vocals, Burgess, Smith and Van Story recall the glory days of early rock with plenty of spirit dusting off classics like "That's Alright Momma," "You're a Heartbreaker" and "Ubangi Stop." Unfortunately, an unflattering sound mix and several throwaway tunes detract from the band's overall performance. More important, a genuine sense of the fun and the enthusiasm this group projects onstage is never sustained for very long.

Like Toups and the Sun band, Barrence Whitfield & The Savages are best appreciated in concert. An old-fashion, highly kinetic soul shouter, Whitfield likes to hurl his voice into a frenzied orbit, but his singing bears an almost heavy metal shrillness on the band's new EP, "Call of the Wild." Consequently, the best songs on the record are the more subdued performances like "The Apology Line," which features the Savages pursuing a rather straightforward approach to modern R&B.

Finally, "Return of the Thin Man" heralds the comeback of veteran R&B saxophonist Noble "Thin Man" Watts, and it's by far the most consistent album of the bunch. Backed by a soulful band, Watts plays an even more soulful tenor on tunes like "Slow Draggin' " and "Nobility." Elsewhere, he alternates the cool funk of "Bad Bitch" with swinging and surging honkers like "Skunky." In fact, unlike the other bands mentioned here, Watts may even have some trouble duplicating onstage all the warmth and energy he pours into the finest selections here. WAYNE TOUPS --

"ZyDeCAJUN" (Kajun 5032).

SUN RHYTHM SECTION --

"Old Time Rock & Roll" (Independently produced cassette).

BARRENCE WHITFIELD & THE SAVAGES --

"Call of the Wild" (Rounder Europa-Reun 1029).

NOBLE "THIN MAN" WATTS --

"Return of the Thin Man" (King Snake KS 003).

All appearing Saturday with several other bands at the Blue Bayou Music Festival at the Prince George's Equestrian Center in Upper Marlboro. 952-4740. (Also, the Sun Rhythm Section performs Friday at the Twist and Shout Club, and Wayne Toups will be there Saturday. 587-4352.)