A string quartet was born full-grown last night at the Smithsonian. The Smithson String Quartet (named after the institution's first benefactor) played its premiere as though its members (Jaap Schroeder and Marilyn McDonald, violins; Judson Griffin, viola; and Kenneth Slowick, cello) had been performing together for years. There was a spontaneous unanimity, a blend of tones that still left each voice distinct and recognizable, a shared affection for the music (all by Haydn) that conveyed precisely what chamber music is all about. The program will be repeated tonight, and there will be three more during the season -- the first of many such seasons, we may hope.

The Smithson Quartet plays on four old instruments from the Smithsonian collection that (unlike the Stradivari played by the Juilliard, for example) are still in their original condition, using gut strings and tuned at 18th-century pitch, somewhat lower than modern. The sound has a natural mellowness that is as pleasant as it is authentic. The four instruments are not a "matched set" like those used by some other quartets. They were made in four different workshops in four different Italian cities, with a gap of more than a century between the 1670 Amati played by Schroeder and the 1783 Gragnani played by McDonald. But in the hands of these four players, they sound like they were made to be played together.

If the Smithson String Quartet was born fully mature, the music it played last night was not. The program began with Op. 2 No. 1 in A, which was actually a five-movement divertimento with two minuets and a figured bass played by harpsichordist James Weaver. Sophistication had increased tremendously by Op. 17 No. 1 in E, and in the final work on the program, Op. 54 No. 1 in G, the form had reached robust adulthood, if not its ultimate possibilities. The later quartets were beautiful, of course, but even the tentative beginnings were charming in this performance.