Richard Wagner's "Der Ring des Nibelungen" is a formidable achievement, tales of Germanic and Norse myth told in four operas fraught with incest and lust, conspiracy and betrayal, theft and lies, hatred and murder, and eventually love, forgiveness, compassion and redemption.

That PBS is airing all four -- "Das Rheingold," "Die Walkure," "Siegfried" and "Gotterdammerung" -- this week is also a formidable achievement. In fact, televising the Metropolitan Opera's production on four consecutive evenings is the largest opera telecast ever undertaken in American television.

Wagner originally wanted "The Ring" to be performed on four consecutive evenings, but doing so proved exhausting for the singers and conductor. The Met chose to perform the first two in a row, then took a day off before the taxing "Seigfried" and another before "Gotterdammerung." James Levine, the Met's artistic director, conducted all four.

The Met's production was first seen during the 1988-89 season, prompting Donal Henahan of The New York Times to remark that "the entire 'Ring' project ... will stand as the decade's finest achievement by the Met and its artistic director."

For PBS's 17 hours of telecasts, Monday through Thursday at 8 each night, host F. Murray Abraham will explain Wagner's dramatic spectacle (subtitled in English) to those who are unfamiliar with the tale. Executive producer Peter Gelb said successive evenings will include introductory scenes recapping previous action.

The story begins with "Das Rheingold," in which Alberich, a Nibelung gnome, learns that whoever forges a ring from the Rhinemaidens' magic gold will rule the world. Ownership of the ring -- and the curse to all who own it -- connects all four operas until the ring is eventually returned to the Rhinemaidens.

Major cast members: Hildegard Behrens as Brunnhilde, eldest Valkyrie and Wotan's favorite daughter; James Morris as Wotan, ruler of the Gods and father of the Valkyries and of the Volsung twins, Siegmund (Gary Lakes) and Sieglinde (Jessye Norman); Seigfried Jerusalem as Seigfried, son of Siegmund and Sieglinde, grandson of Wotan and Brunnhilde's lover; Ekkehard Wlaschiha as Alberich, the Nibelung dwarf, brother of Mime (Heinz Zednik) and father of Hagen (Matti Salminen).

Using Wagner's original stage directions, Otto Schenk has overseen the production, with sets -- including Wotan's fortress, Valhalla -- by Gunther Schneider-Siemssen, costumes by Rolf Langenfass and exceptionally atmospheric lighting by Gil Wechsler.

Brian Large served as television producer. Large, who has directed many of the Met's telecasts, was also TV director of the 1976 production of "The Ring" from the Bayreuth (Germany) Festival. PBS aired the operas over more than four months in 1983.

"Brian Large has done an absolutely superb job," said Gelb. "Our challenge is always to make a television performance as close as possible to being there. Some productions are easier to translate. This one is particularly difficult, although I believe we've been successful.

"My whole goal is to try, without compromising the artistic integrity of any subject, to reach out to the broadest possible audience and to demystify the whole world of opera."

Gelb, son of New York Times editor Arthur Gelb and nephew of violinist Jascha Heifetz, grew up in New York City surrounded by music and theater. Although he said he has had no formal music training, and has devoted the past decade to producing for television (including the Emmy-winning "Horowitz in Moscow"), he said he has become caught up in "The Ring."

After the operas were taped before an audience, more shooting was done of scenery alone with subdued, murky lighting to be edited into the tapes. Then Gelb, Large and the tape editors reviewed the tapes "over and over again. Every time you look at one of these things, you have to prepare yourself for six hours."

But instead of the tedium he expected, Gelb found excitement.

"It's incredible," he said. "The amazing thing about 'The Ring,' the more I've worked on it, the more involved and excited I've become with the operas. They really are extraordinary. They really are musical theater in a true sense. They are much more than operas -- some operas have great music but dramatically are really flat. You can really feel that this was a masterpiece. I'd like to believe, I guess, that this production is the kind of production that Wagner would have liked to have seen mounted in his day, but that technically was not possible ...

"This one works because it is very credible. It's this grand epic myth that unfolds over the course of these four operas. You really get involved with the characters and the emotions. They're very complicated characters, really deep psychological studies. Wotan has a lot of ambiguities about his personality, very tragic, very knowing, very vain, petty -- he's an extremely complicated figure."

The production, he said, "is so accessible, for anything that's so long. I really hope that people who don't see opera will give it a chance. This music finds itself in so many other places -- 'The Ride of the Valkyries,' for example, is in 'Apocalypse Now.'

"All of the way it's being presented on television -- the introductions, the title sequences, even the subtitles -- we try to make as clear as possible."

And because a television audience may get fidgety, he said, "Jimmy Levine got PBS to make the station breaks slightly longer so people will have a chance to stretch their legs."