THE YOUNG Panocha Quartet's first, and apparently only, record of quartet's by Haydn, Schubert and Dvorak, taped back in 1974, finally reached us two years ago (circulating now as Quintessence PMC-7183). And we could only wonder why the release was delayed so long and why this fine Prague ensemble hasn't been recording more. A second recording has just appeared, and, as if by way of certifying the group's status, it is a performance of the Mendelssohn Octet given in collaboration with Czech's senior chamber music organization, the Smetana Quartet, recorded digitally at Tokyo concert last year (Denon OX-7219-ND).

The Smetana's two earlier recordings of the Octet, both made together with the Janacek Quartet, were probably the most admired versions of this marvelous work to date; neither of them has been available for some time. Curiously, there is another digital recording of the Octet, but it is one performed by an orchestral string section (the Israel Philharmonic under Zubin Mehta, London LDR-10009). It is a handsome one in its way, but Mendelssohn's original scoring seems unarguably more fetching, and the new Denon recording is surely the one to have now -- unless you happen to be put off by the applause at the end. In this case I was not, and the audience is absolutley silent throughout the music itself.

Something more unusual, or, at any rate, more unexpected, is the new Laurel Record (LR-116) on which the Pro Arte Quartet performs Beethoven's original version of the Quartet in F major which he subsequently revised to make No. 1 in his first set of quartets, Op. 18. Lewis Lockwood, in his comprehensive notes (a substantial insert, illustrated with musical examples from both versions of the work), points out that "the logic that dictated many of the structural changes forced Beethoven to abandon a number of beautiful and subtle details in the original version," three of whose four movements are considerably longer than in Op. 18, No. 1.

Norman Paulu, the Pro Arte's first violinist, in notes of his own, cites practical considerations which led to the revision, among them one passage near the end of the work with a voicing problem that "could only be solved for the recording with electronic help." The notes by both Lockwood and Paulu are not only helpful but outright indispensable to such a project; one can only be grateful the material is set forth in such clarity and detail.

The performance itself is most appealing, the sound is first-rate, and the actual pressing, on "the new American 'Quiex' vinyl," compares with the best from abroad. In addition to the annotative material on the insert and the liner, there is a chronological chart showing the changing membership of the Pro Arte Quartet from its founding in Brussels in 1912 down to the present group in residence at the University of Wisconsin at Madison. Few may have known of this continuity, or the the group's leader for 23 years (1944-67) was Rudolf Kilisch.

Not quite as expected as a new (or, in this case old) version of a familiar Beethoven quartet, but still in the novelty category nonetheless, is chamber music by Tchaikovsky. His unusual and striking Piano Trio in A minor, certainly not an overexposed work, is represented in two new recordings; its is played by pianist Vladimir Ashenazy violinist Itzhak Perlma and cellist Lynn Harrell on Amgel SZ-37678, and by the Kastman Trip in Turnabout TV 37017.

What is most apparent after hearing and rehearing both performances, which in terms of interpretive approach, is that this work has never been so well served on records before. Both teams play it without either of the composer-authorized cuts, and both play it very persuasively. Both, too, are handsomely recorded.

It is a sort of cliche perhaps, to observe that a threesome that has been performing together regularly gives a more throughly integrated performance than all-stars assembled for the occasion, but the Eastman performance does seem just a bit more all-of-a-piece, just a little more "breathing as one." I would not want to exaggerate the differnce in this respect, for the Angel all-stars are hardly less eloquent or committed, and surely no less exciting; the Chopinesque poetry Ashkenazy brings to the mazurka variation in the long second movement is something quite unmatched in any other recorded performance of the work.