The Smithson String Quartet seems to ply its trade in its own stylish world, unaffected by the traits that characterize its competition, the vigor of this group or the uncanny ensemble of that. Its members are scholars of the classical period in music. The instruments they play are 18th-century instruments and the techniques they play them with are 18th-century techniques.

Their concert last night at the Smithsonian's Hall of Musical Instruments was performed with a gentle elegance that affirmed the intimacy of the chamber ideal without the overtones of virtuosity that so often colors such performances.

A modest but mannered Andantino and an anything but modest violin cadenza at the end of the finale were of particular interest in an otherwise routine quartet by Boccherini. Mozart's "Hoffmeister" Quartet K. 499 featured a lovely sense of ensemble for three movements, but had a final Allegro that had not yet fallen into place. Here the violinists needed to coordinate moving in and out of their syncopations with less fuss.

The program ended with Haydn's G Major Quartet Op. 54 No. 1 played with all the finesse one could ask for, but also with a rather humorless restraint.