For Mozart's 232nd birthday Wednesday, the Smithson String Quartet looked at his growth as a composer and his relations with his model, friend and mentor, Franz Joseph Haydn. The program, given Tuesday and Wednesday nights in the Renwick Gallery, combined a bit of biographical interest with a selection of fascinating music beautifully played.

The evening began with Mozart in 1783, producing the half-dozen quartets dedicated to Haydn that proudly proclaim the elder composer's influence. The Smithson played the intense, beautifully wrought Quartet in D minor, K. 417b.

This vigorous but thoughtful music was followed by the two graceful movements of Haydn's Quartet in D minor, Op. 103 -- the composer's last work, which he began a dozen years after Mozart's death but lacked the strength to finish. It contrasted touchingly with the imaginative energy of Mozart and of Haydn in his prime -- the "Sunrise" Quartet, Op. 76, No. 4, which was played in the second half. But the special flavor of Haydn's personality could be heard in every measure.

Mozart's Quartet in D minor, K. 173, was composed in 1773 when he was 17 years old and obviously under the spell of Haydn's recently published Op. 20 quartets. The Haydn influence is evident, particularly in the fugal finale inspired by three of the Op. 20 quartets, but the voice is clearly Mozart's.

The early, gut-strung instruments blended almost ideally, and there was a special elegance and a strong sense of dialogue among the members of this ensemble, now in its sixth season at the Smithsonian. From a purely scholarly viewpoint, it might have been interesting to include quartets from Haydn's Ops. 20 and 33 that influenced the Mozart works on the program. But it is hard to quarrel with the decision to show Haydn both in his prime and at the end of his career.