The Mostly Mozart Festival from Lincoln Center opened at the Kennedy Center Concert Hall last night with a program that was all Mozart, all delightful and all sold out.

Gerard Schwarz led a Mostly Mozart Festival Orchestra that had an ideal balance of winds and strings, with the winds more prominent than most symphony orchestra proportions permit. It is an orchestra small enough to be credible as a chamber ensemble, but large enough for the demands of the later symphonies, and it is marvelously responsive.

Schwarz concentrated on details, on inner voices and textures, and above all, on broadening lines momentarily. There was the beautifully shaped last note of the "Haffner" Symphony's Minuet, the bit of extra weight at the top of the phrases in the Adagio of the G Major K. 216 Violin Concerto and in the Largetto movement of the C Minor Piano Concerto K. 491, and the accents in the "Haffner's" Finale. These were little touches that added up to something memorable.

Joshua Bell was the soloist in the Violin Concerto and had the unenviable task of living down the "whiz kid" label. This he did with a display of artistic maturity and uncompromising technical excellence that spoke eloquently for itself. Uncharacteristically, for a young performer, his most powerful playing came in the slow movement of the Concerto where his strengths of unusual concentration and patience were most evident. He was able to wait until the last possible moment to resolve a cadence, to give each line space to breathe and still to maintain an integrity of movement and direction that allowed the music to grow. It was an impressive display of musicianship.

Horacio Gutierrez was the soloist in the Piano Concerto and, while he dwelt carefully on each note, he projected a sense more of premeditation than of joy and freedom. This was a serious, studied performance and one that was interesting, rather than lovely.

The concert opened with a fleet, if not always crisp, performance of the Overture to the "Marriage of Figaro."