The Lindsay String Quartet, a British ensemble still little known here, played an outstandingly musical recital at the Library of Congress last night.

The performances were all the more impressive because they were in the Coolidge Auditorium, principal home for more than two decades of the Juilliard Quartet. For all their stylistic differences, each group has an uncompromising seriousness -- but not always sobriety -- in its approach. In neither case is there a trace of that polished gloss for its own sake that some of their musical peers substitute for substance.

The program's novelty was the first of four quartets by Sir Michael Tippett, now probably Britain's dean of composers and a person with whose works the Lindsay has become as closely identified as was the Juilliard with Barto'k in its first years.

Tippett's quartet, dating from 1935, is a strong one. The style might be called Shostakovich and beyond -- referring to further harmonic and rhythm explorations the Russian master might eventually have taken had he not been deterred by the commissars (most Shostakovich quartets actually came after this one).

An example of the Tippett manner: The rapt opening of his deep, reverent slow movement (the main one) recalls for several measures the bars that open the hymn of mourning at the end of the first movement of Shostakovich's "Leningrad" Symphony -- the Shostakovich is of such beauty that it somewhat obviates the banalities littering that piece of musical propaganda.

Tippett's theme, however, moves in other, more elusive, directions -- still preserving, though, a deep sense of benediction. From the very solo transition that leads into it from the athletic first movement, through to its hushed end, the performance -- opulent textures and all -- was eloquently sustained.

One of the keys to the Lindsay Quartet's emotional power is the intensity of its quiet playing, nowhere more impressive than in the great variations on "Death and the Maiden" -- magnificent studies on the nature of grief -- that are at the center of Schubert's D minor quartet by the same name. Last night, this movement was all the more striking in juxtaposition with the breathless drama of the Lindsay's opening movement.

The ensemble opened with a playing of Haydn's Quartet in E flat, Op. 33, No. 2, which mixed his combination of musical purity and audacity to perfection.