THREE STRONG conductors are active now in East Germany and, not at all surprisingly, they are linked by the common bond of Beethoven. Kurt Sanderling, the elder statesman, holds the distinction of having made the first digital recording of all the Beethoven symphonies (for EMI). Otmar Suitner is completing the cycle for Denon. Kurt Masur, the youngest member of this triumvirate and the one now emerging as an international celebrity, made an analog set of the symphonies about a decade ago that received raves in Europe but so far has not made its way to our country. Now Masur has become the first of these conductors to record Beethoven's solitary opera; his "Fidelio," digitally mastered, has been issued in a three-disc Eurodisc set (300.712-445).

Masur's way with the opera is not ablaze with revelations, not supercharged with "philosophical" intensity. It is, however, an exceptionally cogent, "takes-you-where-you-want-to-go" approach, and on the most solid ground both musically and dramatically. The orchestra is his own, that of the Leipzig Gewandhaus, with the city's Radio Chorus and the men of the (East) Berlin Radio Chorus. The cast is a fine one and works well together.

The American soprano Jeannine Altmeyer sings Lenore, Siegfried Jerusalem is Florestan, Siegmund Nimsgern is the Pizzaro and Theo Adam is Don Fernando. The less familiar Peter Meven makes an especially strong impression as Rocco, and the roles of Marzelline and Jaquino have been assigned to singers (Carola Nossek and Ruediger Wohlers) who take them seriously enough to make even the opening scene seem more than dispensable padding.

I've enjoyed returning to this "Fidelio," not for the flaming insights of Kurt Masur but for the solid strength of Beethoven's conception as honored by Masur. Because a good deal of dialogue is included (enough to make dramatic sense, not enough to get in the way of the music), three discs are required, and there is room for Masur's performance of the "Lenore" Overture No. 3. Since on records there is no need to fill time while a stage set is being changed, this is not inserted between two scenes of Act II, but is tacked on as a filler, at the end of side 6.

Happily, there is not a single unsatisfying "Fidelio" among the seven current stereo recordings. For me, the choice now comes down to the noble Klemperer version on Angel and the new Masur; if pressed to choose one or the other I'd probably go with Masur.

Elisabeth Soederstroem, the superb Swedish soprano who gave a song recital in the Kennedy Center's Terrace Theater last January, has been recording Rachmaninoff songs with Vladimir Ashkenazy as her accompanist, and Janacek operas with Sir Charles Mackerras conducting, but has not recorded any of her great Strauss roles. Indeed, the only one she has sung in this country was that of the Marschallin in a Houston "Rosenkavalier." On a new EMI import (ASD 4103), Soederstroem may be heard with the Welsh National Opera Orchestra under Richard Armstrong in the Marschallin's Monologue, the closing scene of "Capriccio," and the "Four Last Songs."

The Countess in "Capriccio" is one of Soederstroem's finest roles; lacking a complete recording, it is good to have this souvenir, in which Philip Joll is heard as the Major Domo. The "Four Last Songs" constitute a memorable side, even if Soederstroem's voice now lacks some of the sheer radiance of Kiri Te Kanawa's, as heard in the latter's Strauss collection with Andre Davis conducting on CBS.

Te Kanawa appears again on a London disc of Mozart concert arias, with the Vienna Chamber Orchestra under Gyoergy Fischer. This is the same material that was released last year as the first of the five records in the Time-Life collection of Mozart's 35 soprano arias (the other four featuring different singers); may listeners will welcome the opportunity to enjoy these seven beautifully sung arias on their own. They are: "Ah, lo prevedi!" (K. 272); "Vado, ma dove?" (K. 583) and "Chi sa, qual sia" (K. 582), both for Martin y Soler's "Il burbero di buon core"; "Oh, emerario Abrace" (K. 79); "Non piu, Tutto ascolati" (K. 490), a 1786 addition to "Idomeneo"; "Bella mia fiamma" (K. 528), and the charming "Nehmt meinem Dank" (K. 383).