The Smetana Quartet of Prague, working its way through its second cycle of the Beethoven string quartests in a series of recordings taped quadraphonically by Supraphon and digitally by Nippon Columbia in its Denon series, has just completed the Op. 18 set with a pairing of No. 3 in D major and No. 6 in B-flat, taped last May and issued now on Denon OX-7138-ND. These are two glorious performances, quite possibly the finest ones of any music the distinguished Czech foursome has yet recorded, and the sound is incredibly spacious and well balanced.

The B-flat Quartet has some pretty zippy tempos in this version, but they do not seem exaggerated, and the prevailing impression throughout the two works is one of great elegance as well as great vivacity. The Supraphon quadro disc has not materialized so far, but I can't imagine forgoing the pleasure of what Denon has given us, on absolutely silent surfaces, for the dubious advantage of four-channel playback.

The two earlier installments in the Semtana Quartet's Beethoven cycle are Op. 18, Nos. 2 and 4, on OX-7077-ND, and Nos. 1 and 5 on OX-7105-ND. The "Rasumovsky" quartets should begin appearing in a few months; the high standard of the Op. 18 set encourages the highest expectations.

In the meantime, one of the Smetana Quartet gems from the recent past has been reissued on Quintessence PMC-7101. Here three members of the quartet, with Pianist Jan Panenka and Bassist Frantisek Posta, give us what is very likely the most appealing of all the many attractive recordings of Schubet's Trout Quintet, which the full-strenght foursome follows with a stunning account of the Quartettsatz in C minor. (The Quartettsatz is labeled her "Allegro in C minor from String Quartet No. 12"; it is of course all there is of No. 12 and is usually so identified.)

This package, one of the real gems of the chamber music discography, was recorded in 1960 and was circulated here a half-dozen years later on CBS's shortlived Crossroads label. The new transfer is not quite as bright as the Crossroads', and it is marred by what sounds like a momentary variance in tape speed in the opening chord of the Trout , but it is good enough to be enormously welcome all the same, and the surfaces are first-rate.There also is a cassette edition, which I haven't heard, P4C-7101.

At the same time Quintessencerevived this marvelous Trout , Philips got round to the first American release of a fine version it has had in its European catalogue for a dozen years or more, offered on its mid-price Festivo label (6750.115; cassette 7310.115). It is played by the Grumaiaux (string) Trio, with pianist Ingrid Haebler and Bassist Jacques Cazauran, and the performance exhibits all the virtues one expects from Arthur Grumiaux and his associates. Between this one and the Quintessence, though, I would not hesitate to choose the latter, even with its blurred opening, for, as I have already remarked, that version is in a very special class. Moreover, it is priced lower than the Festivo release, and Festivo offers no filler, while the Smetana Quartet's performance of the quartettsatz is as outstanding as that of the Trout itself.

Both vocal and instrumental chamber music by Ravel may be heard on a new Nonesuch disc (H-71355), which displays both imaginative programming and exemplary musicianship. Mezzo Jan de Gaetani gives an exceptionally evocative performance of the Chanson madecases with Paul Dunkel, flute, Donald Anderson, cello, and Gilbert Kalish, piano; violinist Isdore Cohen and cellist Timothy Eddy are so persuasive in their realization of the Sonata for their two instruments that one must wonder how so beautiful a work continues to be so little known; finally, Kalish and Paul Jacobs perform two of Ravel's works for two pianos: the Sites auriculaires of 1897 and the brief Frontispice of 1918.

Sites auriculaires comprises two pieces, the original version of the Habanera which found its way into the orchestral Rapsodie espagnole 10 years later, and a shorter number called Entre Cloches , which never appeared in print during Ravel's lifetime. Frontispice calls for five hands, and the fifth one in this performance is, one might well say, the guiding hand of Nonesuch Records: it belongs to Teresa Sterne, known and admired throughout the record world for her tasteful and creative direction of this label's destinies.