It is not exactly the businest week of the musical year, but there isone current event that would be special at any time. On WEdnesday, the Summer Operat Theater Company is producing Leos Janacek's intense, searing opera tale of adultery and suicide, "Katya Kabanova," which he introduced in 1921. It is the first of the great works of Janacek's remarkable final period, when most of his greeatest music was written, after he started an adulterousrelationship with a woman almost 40 year younger than he was. Performed at Catholic University's Hartke Theater, "Katya" will be repeated Friday and next Sunday.

Other notable events: two National Symphony Orchestra concerts at Wolf Trap. On Friday night Gunther Herbig will conduct, with the Labeque Sisters playing piano, and on Saturday the conductor is Mitch Miller. DANCE

The Paris Opera Ballet gives the final performance of its current visit this afternoon at the Kennedy Center Opera House, repeating "SwanLake" with a last new cast of principals -- Isabelle Guerin as Odette-Odile; Charles Jude as Prince Siegried; and Rudolph Nureyev as the Tutor-Rothbart. FILM

Tuesday at the Library of Congress' Mary Pickford Theater, "Unfaithfully Yours," Preston Sturges' remarkable tapestry of music and comedy.

Tuesday and Wednesday at the Sudwell Cinema, Francois Traffaut's "Jules and JIm."

The free summer cinema series continued tomorrow at the National Theatre with Ingrid Bergman in "Anastasia."

Among current releases, "Aliens," which gets your heart pumping, and "Heartburn," which breaks it. POP MUSIC

The annual Bull Run Country Jamboree's a good 'un this year, with Reba McEntire's hard country and Lee Greenwood's soulful ballads topping a bill that includes the Forrester Sisters and Mel McDaniels. AtBull Run Regional Park today.

The reconstittued X (Dave Alvin replacing Billy Zoom on guitar) makes its first Washington appearance, a club date at the 9:30. On Tuesday.

Lou Reed. His life was saved by rock 'n' roll. Of course, his life also was risked by rock 'n' roll, but he's survived and continues to surprise. At Merriweather Post Pavilion on Tuesday.

Thepolitics can wait, the movies will get made. On Tuesday and Wednesday, Harry Belafonte will be singing at Wolf Trap.

Bob Seger still holds to the code of the road and heartland rock 'n' roll. He makes his first area concert appearance in three years at Merriweather Post Pavilion Thursday and Friday.

Mick Taylor, the last Rolling Stones guitarist to leave the group alive, brings his new band to the East Side Thursday.

The Kennedy Center's not exactly Newport, but the frame of the festival is familiar; many talented acoustic musicians and singer songwriters, some well known (Taj Mahal, Richard Thompson, the Roches, David Bromberg, Richie Havens) and some who will be (David Massengill, Chrtine Lavin, Greg Brown). There are two concerts on Saturday and another one next Sunday. THEATER

For anyone who came of age during the 1960s, "Beehive" (at Arena's Kreeger Theater) strikes all the right chords. Here, recaptured by a talented cast of six, are the female vocalists and girl groups that presided over the decade. If you wept with Lesley Gore, were inflamed by Tina Turner, felt for Connie Francis or drooled over the Supremes, you'll be right at htome. The show, which takes its name from the towering hairdo that enjoyed a brief vogue back then, is also a living catalogue of delierious fashions and syncopated dances.Did we really carry on like that? Apparently, we did.