FOR THE last 15 years, the Tatrai Quartet of Budapest has been working its way unhurriedly through all the string quartets of Joseph Haydn on Hungaroton Records. While another such project or two has been begun and brought to completion since the Tatrais initiated their series, they have continued at their own pace, and every installment has seemed worth the wait. So far they have given us the 32 quartets distributed in Opp. 17, 20, 33, 64, 76 and 77, plus the quartet version of "The Seven Last Words" (Op. 51). Now they have added the six quartets of Op. 50 (SLPX-11934/36, three discs).

As in their earlier sets, the Tatrais show a marvelous feeling for the style and spirit of these works. Their knowing approach could serve as a sort of thorn for the interpretation of Haydn's chamber music. But it would be unreasonable to expect that any foursome be capable of withstanding all challenges throughout a cycle of works so exalted and so vast. And for the second time the Tatrais, I think, must take second place.

A year or two back, it was the Juilliard Quartet's set of Op. 20 (the so-called "Sun" Quartets) for Columbia that proved to be, if only by a hair, more persuasive than the Tatrai version. For Op. 50 the issue was decided a little earlier, when Deutsche Grammophon issued its set with the Tokyo Quartet (2709.060). Fine as the Tatrai performances are, they seem a little prosaic in the face of the extraordinary liveliness the young Japanese players brought to this music. Many listeners, of course, like to have more than a single version of such works, and enjoy alternating the Tatrai and Juilliard Op. 20, but in Op. 50 the Tokyo performances are simply too compelling to allow for alternates. Few recordings of any composer's quartets have been so all-round satisfying.

Another ongoing "integral" quartet cycle now facing a serious challenge from a young American-based ensemble is the digital remake of all the Beethoven quartets by the Smetana Quartet for Demon. The Smetana Quartet has been working its way through Beethoven in numerical order, one disc at a time and in addition to the advantage of the fine digital recordings, these recent performances (the sessions began in the summer of 1976) do not rest on tradition but are alive with an imaginativeness, wit and probing quality that seem to reflect especially well the character of these works and the man who created them. Having completed the Op. 18 set some time ago, the Smetana Quartet has now completed Op. 59 (the "Rasumovsky" set) with Op. 59, No. 3, in C major, which is paired with Op. 74 in E-flat on Ox-7188-ND.

I am tempted to say this is the finest record this distinguished quartet has made so far, of Beethoven or any other music. It is certainly the most stunning account I know of Op. 59, No. 3 -- with the mixture of compassion, lyricism and tension so perfectly balanced and the playing itself on the very highest level -- and if there is a significantly more persuasive version of Op. 74 I haven't heard it. I have heard one as persuasive, though, played by the Cleveland Quartet in its set of Beethoven's "middle" quartets (RCA ARL4-3010).

It is the Cleveland Quartet, I think, that provides the real challenge to the Smetanas, but it is the sort of challenge that cannot really be resolved or decided because both groups are so extremely fine and the music itself is so incredibly rich that no single approach can mine all it has to yield. Because of these considerations, many collectors will want to have both the Smetana and Cleveland Beethoven; and because both are so remarkably satisfying, no one could be at all unhappy with either.

It will become more interesting, of course, when both the Cleveland and the Smetana get into the late quartets, as they are about to do. In the meantime, it can be said that the Smetana series boasts superior sound and can be bought one disc at a time, while the Cleveland cycle is less expensive overall, is recorded quite handsomely in its own right, and offers one clear advantage in the form of the exhaustive and stimulating annotations by the group's cellist, Paul Katz.