DOCTOR NIGHTLIFE may have to exercise her First Amendment footwork at Freedom of Expression at the Roxy Saturday ($7; 202/296-9292) because while a reggae band from Nashville may still be a contradiction in terms, you gotta start somewhere. On other beats: FRIDAY

EAGER BEAVERS -- You know what they say: Imitation is the sincerest form of flattery. (Also translated as: If you must copy, do it only from the best sources.) John Cafferty & the Beaver Brown Band started out as the first and perhaps most successful Springsteen sound-alikes; not so prominent now, perhaps, they're still what a good beach-bar band oughta be (at Zaxx in Springfield: $10, 703/569-2582). SATURDAY

LONGHAIRED JAZZ -- It may be set up in the classical style -- two violins, a viola and cello -- but the Turtle Island String Quartet is primarily a jazz foursome. That and a little bluegrass, Texas swing, African and Oriental, whatever comes to hand. You might think of it as the San Francisco version of the Kronos Quartet, except instead of "Purple Haze," they play "Crossroads" (at the Barns of Wolf Trap: $14, 703/938-2404 or 202/432-0200).

FOLK MUSIC'S EXTENDED FAMILY -- The list of performers at the annual World Folk Music Association benefit at GWU's Lisner Auditorium, this year marking the 30th anniversary of Dick Cerri's "Music Americana," evokes 30 years of acoustic music: the Highwaymen ("Michael" was 1961), Sylvia Tyson, Tom Paxton, Bob Gibson & Hamilton Camp, Josh White Jr., Schooner Fare, Carolyn Hester, Steve Gillette & Cindy Mangsen, Pete Kennedy, Fat City, Side By Side and Ticket Back ($25; 202/244-1543). SUNDAY

ON THE INDIE TRACK -- So who needs a Hollywood agent? "Four on the Floor," a CAPO (Capital Area Performers Organization) showcase at the West End Dinner Theatre in Alexandria, features four area bands who have struck out on their own by releasing albums on local labels: the Essentials, Peligro, the Revellaires and Pleasure ($8; 703/370-2500). It's a showcase, but not necessarily a sitdown affair; wear your dancing shoes.

OLD MAN OF THE MOUNTAIN -- When you talk about having roots, you're talking William Lee Golden. After 20 years with the Oak Ridge Boys, during which he spearheaded their transformation from gospel to country, Golden was ousted and then struck out on his own -- as a solo performer, and as a member of the American Mountain Man Association, a back-to-nature group which has adopted Native American rituals (and abandoned the shave-and-a-haircut bit). He's on the comeback trail, too; Golden and a couple of his sons (Rusty and Chris, who used to record as the Goldens) play Zed in Alexandria (703/768-5558). MONDAY

KING OF JAZZ -- It's a living memorial -- more than 100 jazz artists and bands, traditional, blues, big band and contemporary, assembled at Howard University's Blackburn Center, 2400 Sixth St NW, for Lettumplay's round-the-clock salute to Dr. Martin Luther King Jr. Admission is free, and music starts at noon; for more information on call 202/806-5689 or 202/806-5693.

X MARKS THE SHOT -- On the other hand, we don't think Public Enemy's brand of match-the-madness rap rock suits King's rise-above-it style, but the rest of you can get down to it: whether or not it's long, it's definitely strong. Public Enemy DJ di tutti DJs Terminator X shoots the works at the 9:30 club ($10; 202/393-0930).

BLACKBYRDS, FLY -- They were a combination of jazz, funk, rock and a little be-bop -- the Blackbyrds, Washington's own great right-on hopes of the dance-hot '70s, whose Oedipal relations to producer Donald Byrd finally shredded the band. But after 10 years, drummer/vocalist/spokesman Keith Killgo has put together a Blackbyrds reunion at his home stand Takoma Station. The Blackbyrds walk again in rhythm through Wednesday (202/829-1999). TUESDAY

HOME TIME -- Local piano-bar favorite and Mad Romance vocalist Pam Bricker steps out front for a Blues Alley showcase ($12; 202/337-4141). WEDNESDAY

OLD MAN OF THE DELTA -- When it comes to beards and hair and beads and fringe (and talent), Leon Russell probably has Bill Golden beat. And when it comes to eclectic . . . The sometimes Mad Dog, Delta rocker and general e'minence grise of rock 'n' roll (his "Hank William's Back" album exposed a whole new generation to the country roots great) plays a solo performance at the Birchmere ($18; 202/432-0200 or 703/549-5919). THURSDAY

FAST FORWARD -- Think folk music is simple-minded? Jackson Braider has a master's in folklore and mythology from UCLA, has taught both music and folk literature, and writes music to engage the mind as well as the ear. Braider, Jack Hardy, Brian Rose, Lilly Palmer, Wender Beckerman and AV (Vicky Pratt Keating and Jay Keating) are featured at a Fast Folk magazine showcase at the Folkal Point in Ellicott City ($7; 301/982-0686).

FAST FINGERS -- And yes, it's still on -- dueling guitars at the Barns of Wolf Trap with the fully recovered Charlie Byrd & Pete Kennedy ($12; 703/938-2404 or 202/432-0200).