IN 1972 Nippon Columbia introduced digital recording to the world with the creation of its Denon label. Last year, to celebrate its 10th anniversary, Denon undertook a number of major projects with its various European associates, and three especially attractive products of those sessions have just been issued.

First, there is a new two-disc set on which Otmar Suitner conducts the (East) Berlin State Orchestra in Beethoven's Ninth Symphony, with the Second on Side 4 (OX-7257/58-ND). This is a rare instance of duplication in the Denon catalogue, which for a half-dozen years has had a fairly impressive Ninth recorded live in Tokyo by Valclav Neumann and the Czech Philharmonic, with the Prague Philharmonic Choir and four Czech soloists.

Suitner, too, has a well-known Czech singer in his solo quartet, the soprano Magdalena Hajossyova. Her three partners are lesser-known but most attractive German singers--Uta Priew, alto; Eberhard Buechner, tenor; Manfred Schenk, bass--and the chorus is the fine one from the East Berlin Radio. This new recording is superior to the Neumann in every respect, and it belongs in the select group of recommendable Ninths.

As in the earlier installments of his Beethoven cycle (Symphonies Nos. 3, 5, 6 and 7), Suitner is generous with repeats, scrupulous in his respect for the score, and allows the music's passion, tenderness, wit and drama to unfold naturally, without obtrusive interpretative gestures. The Second Symphony comes off as a model of classical balance, and the sonic focus is extremely realistic.

The other two releases, both devoted to music of Mozart, are available on compact discs as well as conventional LPs. The one on which the Smetana Quartet plays the Quartets Nos. 15 in D minor (K. 421) and No. 17 in B-flat (K. 458, the "Hunt"), is not only a duplication of titles but a remake by the same performers. This distinguished foursome's earlier pairing of these two works was one of Denon's first recordings, in 1972; the 1982 remake, issued now (LP: OF-7037-ND; CD: C37-7033), is nothing less than a landmark in the overall chamber music discography.

One first notices the conspicuous improvement in the sound itself. The 1972 recording was very good, but the new one is much richer, warmer and altogether more lifelike. What it conveys is an even mellower and more refined performance than the already excellent one of 1972--and this time the repeats are taken in the outer movements of both works.

Heretofore my choice among all recordings of the "Hunt" was on yet another Denon release, played by another Czech ensemble, the Panocha Quartet (OF-7004-ND, with K. 575). The new version by the Smetana, though, surpasses all previous entries, and I hope Denon will follow through with remakes of the other four quartets Mozart dedicated to Haydn.

Repeats in the outer movements are features of another new Mozart issue from Denon, Herbert Blomstedt's stunning accounts of the Symphonies No. 40 in G minor (K. 550) and No. 41 in C major (K. 551, the "Jupiter") with the Dresden State Orchestra (LP: OF-7041-ND; CD: 38C37-7022).

Blomstedt favors the first version of K. 550, without clarinets, and the repeats, in his performance, do add to the work's "spiritual dimensions," not just its length. In the "Jupiter," the repeats are similarly effective in underscoring the grandeur of Mozart's conception. One is tempted to remark on the "Beethovian" proportions, but Blomstedt never lets us lose sight of the thoroughly and uniquely Mozartean impulse that brought this magnificent work into being.

The great Dresden orchestra is at the top of its form here. The "Jupiter" runs a bit longer than 35 minutes, but fits on a single LP side without a hint of crowding. The sound, in fact, is transparency itself on both sides, and warm and vivid as well.