Despict many commendable aspects to yesterday's Washington debut by the Delos String Quartet at the Phillips Collection, the overall result proved less than inspiring. Currently in residence at the University of Delaware, the players had returned the night before from a European tour. For their introductory program here they chose a handsome mixture of Mozart, Webern and Ravel.

The fundamental problem stemmed from the ensemble's inability to respond to the underlying thrust of the music. Mozart's creative agility in the E-Flat Major Quartet, K. 428, did not spark a matching interpretive quickness. The flowing lyricism of Ravel's F-Major Quartet failed to generate a similar fluidity in performance. Webern's Six Bagatelles, Op. 9, fared the best, in part because its highly compressed writing -- the entire work is only 58 measures long -- sets a more rigid framework.

Clearly, all four artists are intelligent, dedicated musicians who have developed a strong sense of ensemble and a spirited discipline. Their playing has a vigorous immediacy, which does not, however, translate into sustained expressive results. They need to dig more deeply into the composers' language, to search for clues to their deepest intent and find those details that make the difference between an acceptable interpretation and a transcendent one.