ACOUSTIC entertainment varies wildly around D.C. -- from next Tuesday's long-soldout Peter, Paul & Mary benefit at the Kennedy Center, to the Sunday night square dances and concert series of the tradition-conscious Folklore Society of Greater Washington, to the "top-40 folk" you can listen to (or, like most of the folks at the bar, ignore) at any of a dozen or more saloons around town.

Look around. If you want to listen, take your ears here:

THE BIG TWO

THE BARNS OF WOLF TRAP -- 350 seats at 1551 Trap Road, Vienna. 255- 1800. A happy amalgam of low-maintenance, rough-hewn atmosphere and low- key, high-standards production (plus relatively cheap drinks and comfortable seats) makes this a consistently good place to find touring acoustic types relaxing and getting intimate. (With their audiences.) Take, for instance, the Whites, and especially Livingston Taylor, last weekend -- or, coming soon: folk/bluesman David Bromberg (Feb. 28); autoharpist Bryan Bowers (March 14); Maine's seafaring folk trio Schooner Fare (March 21); folk veteran and ever-sharp satirical songwriter Tom Paxton (March 22); and singer-songwriters Tom Rush (May 2) and Kate Wolf (May 10). Reserved seating, $7 to $14.

THE BIRCHMERE -- About 300 seats at 3901 Mt. Vernon Ave., Alexandria. 549-5919. Not long after its modest 1977 beginnings, the Birchmere became known, and then renowned, for its attentive presentation of Washington's (and the country's) best bluegrass talent. But bluegrass -- except maybe for the Birchmere's trend-transcending Thursday night regulars, the Seldom Scene -- doesn't draw as well as it used to. And since the Birchmere's purpose is making money (in addition to serving beer, wine and assorted deep-fried things), owner- manager-soundman Gary Oelze now books more folk and new-acoustic acts than bluegrass. And many of the best local and up-and-coming acoustic performers can be seen at Dick Cerri's monthly "Music Americana" showcases here, which draw increasingly large and enthusiastic crowds. Coming: Tony Rice Unit (this Friday-Saturday); Schooner Fare (Tuesday-Wednesday); John Hartford (Feb. 28-March 1); Magpie (March 12); Bill Morrissey with Side by Side, March 15; the Birchmere's first children's show, with Phil Rosenthal and Cathy Fink (March 16, a Sunday, at 1 p.m.); Sylvia Tyson (March 21-22); Fink, Marcy Marxer and Mary Chapin Carpenter (March 28); Mike Cross (April 4-5); Jesse Winchester (April 11-12); Schooner Fare (April 18-19); Guy Clark (April 26). Open seating, $5 to $15.

FURTHERMORE: Lisner Auditorium (for the occasional acoustic concert, such as last month's serendipitous anniversary concert for Dick Cerri, and next month's Tommy Makem and Liam Clancy date, March 15); the Kennedy Center Concert Hall (also for occasional concerts, such as Tom Rush's "Club 47" reunion in January with Emmylou Harris, Peter Rowan, Mark O'Connor and stunning cast of "unknowns," and next week's sold-out Peter, Paul & Mary date); and Ethel's Place, the Baltimore jazz venue that recently began booking folk and acoustic acts about twice a month (including Tony Rice, next Thursday). You might also look for more folk-acoustic dates at other established jazz clubs, including Annapolis' King of France Tavern, and Blues Alley in Georgetown.

SMALL SPACE, BIG CONSCIENCE

FOOD FOR THOUGHT -- 1738 Connecticut Ave. NW. 797-1095. They still pass the hat between sets; sometimes, such as when the intense hat passer is a Mary Chapin Carpenter or a Toshi Reagon, this won't bother you -- and you might even want to donate a larger hat. Last Saturday, Food for Thought actually charged a $3 admission for its 13th birthday celebration, which featured a band, contests and skits by a some of the Public Interest Follies folks.

GALLAGHER'S -- 3319 Connecticut Ave. NW. 686-9189. Never a cover here, but always someone committed to folk/Irish/acoustic musicmaking on stage (if you could call the tiny spot in front of the coffeemaker a stage). Commitment of crowd varies. One of the better open-mike shows in town (Sunday-Monday).

KRAMERBOOKS/AFTERWORDS -- 1517 Connecticut Ave. NW. 387-1462. eclectic, mostly folk and acoustic jazz bookings make this a good place to hang out and discover the kind of low-key, loving-it musicians and songwriters you thought lived only in, say, San Francisco. Since the odd layout places the stage up in the rafters, though, hanging out here too long can lead to neck problems.

TAKOMA CAFE -- One Columbia Ave., Takoma Park. 270-2440. The Takoma Cafe's own Thursday through Sunday night entertainment schedule reflects the folky, folksy nature of the neighborhood, long a hub of homegrown and traditional music in the area. Bookings range from the accessible and heartfelt harmonies of Side by Side's Sean McGhee and Doris Justice (this Saturday) to regular bluegrass/old-timey showcases, with such as Bill Rouse & Uptown Grass (this Sunday) and Red Toad Road (Feb. 28). Most Monday nights, the Cafe is turned into a tiny concert hall by a neighbor: The House of Musical Traditions. HMT's schedule of local and out-of-town pickers, fiddlers and singers includes recent (and packed) shows by Cathy Fink and Marcy Marxer, Boston flatpicker Orrin Star, West Virginia string duo Critton Hollow, and claw- hammer banjo player (and Philadelphia radio folk scholar) Bob Carlin. Other HMT stuff at the Cafe includes dates by local string band Roustabout (this Monday) and the Andean folk group Sukay (April 7). "Most of the money at the door goes to the artist," says HMT volunteer Trina Royar. "We lose money but we do it anyway, because it's a goodwill gesture and it's something we all like -- the sociability, the intimacy, the involvement."

FURTHERMORE: The Potter's House (for an eclectic, coffeehouse setting, with acoustic folk/blues/jazz every Friday-Saturday, including Side by Side March 7); Ireland's Four Provinces (for the Clancy Brothers March 3); the Tucson Cantina; the Dubliner; the Irish Connection; Irish Times; Bosco's, Silver Spring; Murphy's and Tiffany Tavern, Alexandria; Whitey's, Arlington; the Old Brogue, Great Falls.

CONCERT SERIES

FOLKLORE SOCIETY OF GREATER WASHINGTON -- 281-2228. Among the largest and most active such associations in the country, the FSGW has been around 21 years, and its annual -- and free -- Washington Folk Festival (the first weekend of June this year, at Glen Echo Park) is among the most diverse and well-attended on the East Coast. Typically, a half-dozen stages are populated by several hundred mostly local performers -- clogging teams and African storytellers, Brazilian dancers and Appalachian string bands, "new- grass" bands like Grazz Matazz and compelling traditionalists like Celtic Thunder, or singer/guitarist John Jackson, or local fiddler Steve Hickman. Besides the big annual festival (and a mini-festival in January), however, the FSGW mostly tends to its growing membership (now at 2,200) with ongoing, year-round programs -- all open to the public. These include small-scale house concerts (wherein a performer plays a selected member's living room), gospel sings, a regular square dance/contra dance night every Sunday, and a once- a-month concert series (by the D.C. Youth Ensemble March 14, Connecticut songwriter Jerry Rasmussen April 11, and folksingers/folklorists Jeff Warner and Jeff Davis May 9). FSGW also sponsors one or two larger concerts a year -- the next is by Scotland's Tannahill Weavers, April 12 -- and puts out a shamefully informative newsletter 10 times a year.

SMITHSONIAN FESTIVAL OF AMERICAN FOLKLIFE -- 357-1300. Midsummer on the Mall every year; this year spotlighting the folk arts and music of Tennessee, and Japan (June 24-29 and July 1-6).

SMITHSONIAN MUSEUM OF AMERICAN HISTORY -- 357-1300. The museum's various exhibit-related music series are frequently goodplaces to see folk and traditional acts, local and otherwise. The free, exhibit-related programs include several on Saturday afternoon, and the "American Sampler" series, Thursdays at noon. The "Sampler" series this month is tied to Black History Month; in March, its focus is the museum's "At Home on the Road" exhibition, with traditional music and road songs by Washington's Magpie, Marcy Marxer and Warner & Davis.

SMITHSONIAN RESIDENT ASSOCIATE PROGRAM -- 357-3030. Its occasional acoustic/folk outings -- which are not free, and not necessarily related to Smithsonian exhibits -- have been increasingly well-attended since program coordinator Penne Dann first "tiptoed into the folk music scene" and booked the Smith Sisters into the Air & Space planetarium a year ago. More recent programs at the 560-seat Baird Auditorium in the Natural History Museum -- a country-folk performance/demonstration by Patsy Montana and Cathy Fink last October, and a Tom Paxton/Bob Gibson retrospective last month -- have been just as successful, says Dann. Coming (both to Baird): Pratie Heads, a traditional Irish music band from North Carolina, March 16 (St. Patrick's Day eve); and Metamora, July 25.

FURTHERMORE: Baltimore Folk Music Society (301/366-0808; PO Box 7134 Waverly Station, Baltimore MD 21218); Capital Area Bluegrass & Oldtime Music Association (450-4448; 112 Drury Circle, Sterling VA 22170); Greater Washington Ceili Club (PO Box 2445, Alexandria VA 22301; Daily Clog (local clogging newsletter; 6 Rollins Ct., Rockville MD 20852); Irish Folklore Society (770-3124; PO Box 44530, Washington DC 20026). Washington Gaelic League (3549 Quesada St. NW, Washington DC 20015); World Folk Music Association (PO Box 40553, Washington DC 20016).