Fabio Mechetti is not exactly a stranger to National Symphony audiences. The 30-year-old Brazilian has conducted the NSO in family concerts, educational programs, pops concerts and outdoor concerts at Wolf Trap and the Capitol as part of his work in the Affiliate Artists Conductors Program. But last night was Mechetti's prime-time debut, his first performance at the Kennedy Center in the subscription series.

In a well-chosen and carefully balanced program, he fully justified his close association with the orchestra. In Debussy's "Pre'lude a` L'Apre`s-Midi d'un Faune," his poised baton hovered thoughtfully over the music's languid texture, evoking an almost static sense of a warm, drowsy but erotically charged summer afternoon.

Then, with harpist Nicanor Zabaleta, Mechetti found in Ginastera's Harp Concerto a wealth of vivid colors and vigorous rhythms, clearly modern in sound but attractive to conservative tastes. Finally, and most impressively, he explored the thickets of Dvorak's Symphony No. 7 in D Minor, showing a good sense of the music's dramatic power and finding in it a kind of continuity, form and purpose that can easily get mislaid among the melodic riches and emotional postures.

Dvorak's intense but sometimes rambling work shaped up well under Mechetti's firm guidance. The symphony usually pleases audiences because it has a bundle of tunes and wears its heart on its sleeve so fetchingly, but last night the response was deeper, inspired not by the odd striking detail but by the work's overall, structured power.

There were occasional small problems -- coarseness of sound at the beginning of the Debussy (which is not ideal for opening a program) and slight balance inequities in the Ginastera. But they were minor details in a generally fine evening.