Reprinted from yesterday's late editions.

Schubert was not one to let a good melody get away from him without a thorough workout, and Thursday night at the Library of Congress, the Juilliard Quartet plus cellist Bernard Greenhouse had a field day with the lyrical C Major Quinete Opus 163.

If such a thing as a definitive performance of anything is possible, this was close. To say that the ensemble was exemplary, the balance ideal and the tempos beautifully calculated is just to scratch the surface. All of these operated in a context of an infinite variety of shadings and absorption in the sensual loveliness of the musical ideas. They were in rare form.

For an opener, violinists Robert Mann and Earl Carlyss collaborated on Six Duos from a set of 44 by Bartok, marvelous pieces that, within a small framework, exemplify Bartok's eclectic taste in folk music. The performances had an engaging vitality.

This same energy characterized the Mozart "Hunt" Quartet in a B Flat Major K. 458 that followed. This is a favorite of many people who are able to come to decisions about things like that, a quartet whose middle movements, perhaps, outshine the first and last.

The Juilliard is not one-(or four as the case may be) to handle Mozart with kid gloves or to tread lightly through his phrases. There's a full-bodies approach to this music, energetic and urgent, and refreshingly straightforward. It all sounded like very healthy Mozart except the last movement, which had an almost Haydnesque taste about it.