Witold Lutoslawski's "Novelette" is sometimes mournful, with the sound of strings like lost souls wailing witty, with the winds tossing melodic witty, with the winds tossing melodic fragments around like bits of cocktail - party chitchat, punctuated now and then by a brusque punch line from the percussion. It is mysterious, with low winds muttering something indistinct behind a translucent curtain of harp and violins; brillant with big splashes of color and delicate with tiny points of bright light -- a thread of violin melody, a flick of flute, a snap of wood blocks or clang of sharp metal. After one hearing, it may be too soon to call it a masterpiece, but it is absorbing music and enormously eventful.

Three of the work's five brief movements, in fact, are called "Events," and the title suits them admirably. Although it is not explicitly programmatic, the music, given its world premiere by the National Symphony last night in the Kennedy Center, is something like a drama with relatively undefined characters but sharply delineated actions, a climactic structure and some colorful dialogue.

It was applauded very warmly -- and rightly so -- but there was even more applause for the Lutoslawski Cello Concerto that followed it and concluded the program. This work also has dramatic action, structure and dialogue, but in addition it offers well-defined characters -- chief among them conductor Mstislav Rostropovich, who was the cello soloist while the composer conducted.Following a long soliloquy-cadenza in which he moves from the simplicity of a one-note mantra into very elaborate excursions, the cello goes off adventuring, encounters some interesting characters (notably some tough guys in the brass section), gets lost in a crowd, suffers some bruises in combat but emerges triumphant.

The two works, though composed about 10 years apart, have considerable similarity -- partly because Lutoslawski has a distinctive and recognizable style but also, perhaps because they were written for Rostropovich in each of his two identities as cellist and conductor. The concerto seems to have a more tightly focused structure, but that may be because of its relative familiarity from a recording.

None of Lutoslawski's mature music says everything it has to say on a first hearing -- but to a listener open to contemporary idioms it does say enough to invite further hearings.

Last night's performance were very effective in both works, and concerto was doubly enjoyable because it offered a splendid view of Rostropovich the cellist in music specially tailored for him. The orchestra played with gusto, reveling in the varied colors of the "Novelette" and responding to both the soloist and the conductor in the concerto with precision and enthusiasm. Both works give the players a bit of autonomy, which they used effectively, and the brass seemed to take special delight in the concerto's scenario, which allows it to give the raspberry repeatedly to Rostropovich's musical excursions.

The program opened with Dvorak's Symphony No. 6 in D, in a performance which had a few rough edges and did not do much to mitigate the looseknit structure Dvorak gave to his collection of fine melodies. Presumably, most of the rehearsal time was devoted to the Lutoslawski, and the results in performance vindicate that decision.