The music was clearly Mozart and Haydn on Saturday night in Baird Auditorium--actually two Haydns, Franz Joseph and his younger brother Michael--but the sounds were largely unfamiliar. The Smithsonian Chamber Orchestra, using ancient instruments, gave these composers a robust but delicate performance, beautifully balanced in texture and more like chamber than symphonic music in its spirit and atmosphere.

Above all, the sound was a delight--gentler and warmer than that of modern instruments, free from the hard-driven brilliance that became fashionable in the 19th century and often intrudes anachronistically on the music of earlier periods. Michael Haydn's simple, melodious Symphony No. 4 in C opened the program, followed by Mozart's Violin Concerto in G, K. 211, with Jaap Schroeder as soloist and conductor.

In an ensemble with only 11 string players, woodwinds fit into the texture with a smoothness and ease impossible when big orchestras play 18th-century music. Obbligato solos (which were particularly numerous and delectable in Haydn's Symphony No. 8 in G, "Le Soir") emerged from the orchestral sound naturally, without straining or artificially lowering the volume of the other players. Schroeder provided direction without the self-conscious fussing of a virtuoso conductor, and the players performed in an atmosphere of self-disciplined freedom that is ideal for this music.