It was a citified affair that took place in downtown D.C. yesterday on the several Add Arts stages at Library Place, on F Street and at Gallery Place's Center Stage.

Vendors under beach umbrellas hawked leather goods, African-style goods, costume jewelry, clothes, slogan buttons, balloons, headgear and scented oils. A table of handbills urged all to register to vote, awnings shaded the dispensers of Italian ices, Polish sausage, Kung Pao chicken, beer and pop, and smoke curled up from a grill at the "North Carolina Barbecue" table.

The considerable crowd milled at the booths during the breaks and thronged Center Stage during performances under the hot afternoon sun, all of it making up Add Arts '84 -- A Washington Celebration, a festival put together by a huge conglomeration of public and private sector organizations.

Habibateini -- two women in multicolored ankle-length dresses -- interpreted the ancient heritage of Middle Eastern dance. Ribbon-trailing castanets and jangling bells supplemented the canned, upbeat Greek and Armenian music as the pair circled around or quivered in place, belly-dance style. Harmonica player Al Neilsen and guitarist Richard Flynn delivered country blues. The Nubian Dance Company traded call and response, Debra Tidwell belted out a Mahalia Jackson tune and the African Heritage troupe pummeled five drums with hands and sticks while dancers, several of them children, leaped and bounded across the stage.

Poetry was represented by, among others, Chasen Gaver, who led his audience in a finger-snapping "Diana Ross." For other pieces he used such props as a telescoped parasol and a gourd. Scenes from new works of D.C. playwrights were read by the Source Theatre literary committee.

Burnette Tyesko, Larry Hemphill and Derryl Dyson, wheelchair-confined singers from the Voices of Independent Living, a service organization for the handicapped, rendered blues, ballads and jazz standards, backed up by the Carl Grubbs Quartet.

A block away, on a head-high platform about 20-feet square, a bone-shattering contest in modern dance was in process. The improvising participants included the D.C. Breakers, Special Effects and two 8-year-olds, Ben Feipin and John Garrett.

The spontaneous performance to upbeat polyrhythmic percussion showcased the leading edge in terpsichorean movements, including twirls, gyroscopic headspins, serial leap-frogging, four-man tumbling routines, deep-breath vibrations and Frankenstein monster shuffles.

At the other end of the block, Theater Du Jour drew spectators to its bizarre spur-of-the-moment creations.

At Artists' Invitational Graffiti Wall, in Artists' Alley on E Street, a dozen or more works were in progress on window-size sheets of paper attached to the wall of the Lansburgh Center. Tools included brush, crayon, magic marker, a straight-edge fashioned from a Pampers carton and a putt-putting electric airbrush.

Scenes depicted were a pop-art junior superman with wraparound goggles, his huge hand atop a Metro car half his height; the beginnings of a tortured nook and cranny face gazing heavenward; a dark shadowed gnomelike man amidst back-alley ashcan-strewn disorder; an Art Deco, wildly colored Gaiety Theater; a polka-dotted Marcel Marceau face; a James Thurber-like scene of a bearded man with a long-jawed dog examining with magnifying glass the bust of a nude woman; and a lighthouse aswarm with gulls.

Meanwhile, anyone wishing a change of scene but no less of a celebratory atmosphere could head up to the Capitol lawn for the evening's free pops concert by the National Symphony Orchestra under the direction of Eric Kunzel.

As the 12-hour celebration continued, down one street and up another, artists painted at easels, small groups listened to conga players and spontaneous dance broke out. Chalk doodling covered the pavement from the corner of 8th and F streets nearly to D Street, the paintings of D.C. artists were on display in department store windows, and films and videos were screened at the University of the District of Columbia at Library Place.

A frisbee competition was in progress on the Mall, and the Lettumplay Jazz Ensemble, fresh from its appearance at the World's Fair in New Orleans, was cooking in the Lansburgh Cultural Center.

At the corner of 10th and F streets the Trash Connection Junk Band had rhythm going six ways at once using cowbell, milk crates, tambourines, plastic buckets, bass drum, congas, portable keyboard and rapping voice. Over at Center Stage, the Greg Reynolds Dance Quintet performed a piece titled "Washingtoniana" to a Beethoven string quartet.

The D.C. Contemporary Dance Theater offered a stunning dance drama by the duo of Kathy Smith and Adrian Bolton. Smith was equally breathtaking for her high-leaping pirouettes and flexibility of movement in the full company number that followed.

Sound checks, a tuneup and a brief rehearsal by the D.C. Workshop Orchestra entertained a crowd of several thousand waiting at Center Stage for the evening's performers. Then, in one of the day's high-water marks, Muhal Richard Abrams took his place before the 20-member unit he had spent a week whipping into shape. Its execution of a program of Abrams' originals was, with a missed cue or two, polished, its section work precise and its soloists confident.

Abrams directed the band's traffic-jam ensembles with shouts and fist-waving, finger-to-lip hushes and broad smiles. The orchestra roared, vocalists Arnae' and Bryant Bolling got way down on "Blues Forever," drummer Nasar Abadey rocked the bandstand with zeal, and tenor saxophonist Sing Neal brought the house down with an a cappella statement that did everything but speak in tongues.