The Johnson Mountain Boys perform Saturday night at Gaithersburg High School's Newman Auditorium in a benefit concert for the school's instrumental music department. Three of the five Boys being Gaithersburg High graduates, this is the sixth straight year the band has returned for a benefit. (In between they've taken care of a few little things -- like winning the 1984, 1985 and 1986 Bluegrass Music Awards "Traditional Band of the Year" honors, and performing recently at Nashville's Grand Ole Opry.) Tickets are $7 at the door. Call 926-0435. PLAY IT AGAIN, SAW

The next meeting of SAW, the Songwriters Association of Washington, is a Cassette Critique. Arrive by 6 p.m. this Sunday at Murphy's (713 King St., Alexandria) with a cassette recording of a song you wrote, wrapped in three copies of the lyrics, and the following should occur: Singer/songwriter Jonathan ("Sunshine") Edwards, Lion & Fox Studio co- owner/engineer Jim Fox, and independent producer Blink Simmons will listen to it. Then they will critique it, constructively. You don't need to be a SAW member to participate; you can become one, then and there if you're still in the mood after being critiqued, for $25. Call 652-7543 or 682-7361 for more information on this -- or on SAW's annual songwriting contest, which starts next month. THINGS TO DO

1. Soon: Buy tickets for schizo-comic Steven Wright's February 7 date at Warner Theater (with Leon Redbone). Going fast. If you can't make Wright, also strangely entertaining -- but musical -- is next night's show (February 8) at Warner: Kid Creole & the Coconuts. Nice outfits.

2. Monday: See Asleep at the Wheel -- America's hardest-working country-swing band (in case you forgot who currently held that title) -- at the Roxy.