To bring the five-concert Library of Congress Summer Chamber Festival to an appropriately grand end Tuesday night, they played the Schubert Octet -- which is more like a symphony than most symphonies.

There is its length alone -- six movements crammed into about an hour. There is its sound -- a string quartet combined with clarinet, French horn, bassoon and double bass. There is also its indomitable spirit -- expansive, rich, graceful and, except for the dramatic introductions to the outer movements, irresistibly exuberant. The only other work that comes to mind as comparable in the last respect is also Schubert's -- the "Trout" Quintet, which is not a work on quite the scale of the Octet.

The symphony that the Octet most recalls is not Schubert; it is Beethoven's "Pastoral" -- similarly expansive and cheerful. The Schubert is not so compellingly organized, but melodically it is richer.

The players were violinists Alexis Galpe'rine and Bayla Keyes, violist Miles Hoffman (who runs the festival), cellist David Hardy, bassist Frank Carnovale, bassoonist Lynette Diers Cohen, clarinetist Loren Kitt and horn player Anthony Cecere (who had curbed his tendency from an earlier concert to play too loudly).

There were pitch and ensemble problems -- but not enough to undercut the Octet's esprit.

Also on the program was a set of Eight Pieces for Viola, Clarinet and Piano, Op. 83, by Max Bruch. Some of these dark, melancholy movements were quite eloquent -- the Andante con moto and the Allegro agitato, for instance. But with their somber hues, they sounded too much alike to work well as a suite -- a lengthy one. The performance, by Kitt, Hoffman and pianist Bradford Gowen, was splendid.