It happens now and then. The stars have an off day and the second team wins the game. The big guns were scheduled for the second half of the concert at the Kennedy Center on Saturday night, and the audience was primed for the Schubert C. Major String Quintet.

But first there were Schubert's "Der Hirt auf dem Felsen" and Bartok's "Contrasts," to be performed by relative unknowns, pianist Jean-Bernard Pommier, clarinetist Timothy Paradise, violinist Cho-Liang Lin and soprano Beverly Hoch.

Now it is no disgrace to play second fiddle to the likes of Isaac Stern, Pinchas Zukerman and Leonard Rose. In fact, it can be exhilarating, and in this case the two opening works had a flair and an elan that reflected marvelously pointed and agile playing by Paradise and superb ensemble by all. Hoch brought a nice sense of line, fine diction and control to the Schubert, managing the broad legato of the middle section with lovely legato movement. And the Bartok sparkled with an intense give-and-take between the violin and the clarinet.

The air of anticipation beame almost tangible, however, as Stern, Zukerman, Rose and the rest of the quintet, Lin and cellist Peter Howard, paraded across the stage. But this was not destined to be one of those magic nights. Almost from the beginning the ensemble was uneven. Stern seemed to want to exaggerate that the rest wanted to allow to grow more slowly. The music moved just fast enough to sound facile rather than intense. There was ambiguity between what was background and what was foreground; evidence of difficulty in maintaining momentum in the Scherzo Presto, and a lack of focus in the finale. Only in the third movement trio was there a real sense of the splendor of this piece.

Part of the problem may have been the frustration of trying to recreate the intimacy of chamber playing in that most unchamberlike of concert halls, and part may have been that, on Saturday, the chemistry simply was not there