The remarkable thing about the Manchester String Quartet is the accuracy of its label. It is not merely four young players from the National Symphony Orchestra: violinists Hyun-Woo Kim and Holly Hamilton, violist Lynne Edelson Levine and cellist Glenn Garlick. It is a string quartet, an ensemble--in effect, a single performing personality with four heads and eight well-coordinated hands.

It has achieved this status, at the level that meets the very high requirements imposed on string quartets today, after only one year of performing together on local university campuses, in churches, on radio and in the auditorium of the World Bank.

Last night in the Masur Auditorium of the National Institutes of Health, the Manchester String Quartet entered a new phase with the launching of its "Music for Munich" series: three concerts exploring the repertoire that it will perform next month at the 31st International Music Competition in Munich. On the evidence of last night's performances of Haydn, Hindemith and Schubert, it is ready for such a high-level international test, although it still seems very new to be so well prepared.

Last night's performances were notable particularly for ensemble--the almost telepathic communication that keeps four players together, unified in style and well-balanced through the abrupt changes of pace and flavor in Schubert's "Death and the Maiden" Quartet, the intricate counterpoint and the brusque dramatic gestures of Hindemith's Quartet No. 3, and the delicately poised classicism of Haydn's Quartet in D, Op. 76, No. 5.

These three works thoroughly tested the group's stylistic versatility and provoked commendable results in the classical, romantic and modern idioms. The exploration will continue with Smetana and Ginastera on Aug. 18, Mozart, Ravel and middle-period Beethoven on Sept. 1.

Not everything can be perfected in a single year. There were a few moments during the evening when pitch was not quite dead center, and once or twice a single voice was lost momentarily in the ensemble sound, but these problems were never serious. The next item on the agenda, if the quartet is to continue growing as remarkably as it has done so far, will be to develop a more sharply profiled collective personality, the kind of individuality in interpretation that will make a Manchester performance immediately recognizable while remaining faithful to the music.

But this is not something that can properly be worked out through deliberate calculation; it happens when it is ready to happen, if the group is of the right caliber. We may confidently expect such performances to emerge eventually from this group. Meanwhile, whatever may be its fate in Munich, Washington--a prime showcase for visiting string quartets--can be happy with the quality of one that lives here.