TIM O'BRIEN

"Cornbread Nation"

Sugar Hill

"Fiddler's Green"

Sugar Hill

DANNY BARNES

"Get Myself Together"

Terminus

ADRIENNE YOUNG & LITTLE SADIE

"The Art of Virtue"

Addiebelle

The Achilles' heel of the American folk music movement has always been rhythm. Whether we're talking about the movement's traditional branch or singer-songwriter branch, the genre has too often been characterized by an unimaginative, underwhelming strum-along beat. A month ago Tim O'Brien simultaneously released two albums designed to prove that American folk music's best assets -- its narrative and confessional lyrics, its lovely melodies and harmonies -- are bolstered rather than obscured by vigorous rhythms.

O'Brien, born in West Virginia and based in Nashville, is joined on "Cornbread Nation" by such luminaries as Del McCoury, Dan Tyminski and Jerry Douglas, but the most important guests are percussionist Kenny Malone and upright bassist Dennis Crouch. This rhythm section provides a muscular kick to such traditional numbers as "House of the Risin' Sun," "Hold On" and "Let's Go Huntin'," revealing the lust, fear and humor behind the songs' quaint facades. These ancient tunes by anonymous writers are joined by Jimmie Rodgers's "California Blues," Johnny Cash's "Busted" and two O'Brien originals, thus proving the music's continuity.

"Fiddler's Green" features percussion on only four of its dozen tracks, but it proves just how forceful a beat can be generated by a mandolin chop from O'Brien or Nickel Creek's Chris Thile. Once again, a fistful of traditional tunes is supplemented by a couple of country-folk songs (Lefty Frizzell's "Long Black Veil" and Gordon Lightfoot's "Early Morning Rain") and some O'Brien originals. This time the emphasis is on fiddles -- both lyrical and droning, played by O'Brien, Casey Driessen and Stuart Duncan -- but a strong rhythm pushes the melodies ever forward.

O'Brien's balance between sweet lyricism and droning rawness tilts decidedly in the latter direction on Danny Barnes's new album, "Get Myself Together." Barnes, co-founder of the Austin punk string band the Bad Livers and now a key member of Seattle's Americana jazz scene, recorded most of the album by himself, using fiddler Brittany Haas on just four of the 13 songs and bassist Garey Shelton on just five. Barnes wrote or co-wrote nine songs, but his nasal baritone, scratchy banjo and aggressive guitar conjure up the era of pre-Pearl Harbor mountain singers, when storytelling was unflinching and dance rhythms were irrepressible. Barnes's tales of drunken ecstasy and drunken desperation fit right in between the Blind Willie Johnson hymn, "Let Your Light Shine on Me," and the Rolling Stones' incantation, "Sympathy for the Devil."

Adrienne Young & Little Sadie is another rhythm-driven string band, and its second album, "The Art of Virtue," borrows members from the Del McCoury Band and the Rodney Crowell Band to keep the picking kicking. Young, a Florida native based in Nashville, is an inconsistent songwriter with a modest soprano, but when she avoids easy sloganeering and concentrates on detailed storytelling, as she does on "Rastus Russell" and "Wedding Ring," she can be quite enchanting.

-- Geoffrey Himes

Appearing Friday at the Birchmere.