The role of Tristan in Richard Wagner's "Tristan und Isolde" is generally -- and correctly -- considered the most strenuous part for tenor in the standard operatic repertory.

The man originally intended to sing the first performance, George Ander, who had previously created the role of Wagner's Lohengrin, went mad while studying the part, and Ander's replacement, Ludwig Schnorr, died of a heart attack a month after the premiere, at the age of 29.

Placido Domingo -- the Washington National Opera's general director and an artist with more than 115 roles in his repertory -- considered singing Tristan at the Vienna State Opera in the early 1990s but finally decided it would be too wearing. "I could do it," he told me after he had bowed out of some preliminary talks concerning a production. "I could sing Tristan, I think, but if I did it in the opera house, it might be the last thing I ever do sing!"

Indeed, "Tristan und Isolde" demands stentorian power and near-Herculean endurance, and usually the effort shows. Simply getting through the score, singing above the huge Wagnerian orchestra and projecting out to the back row over the course of three long acts, is an accomplishment in itself. Most tenors end up straining and shouting. But it has long been thought that Domingo had it in him to actually sing the opera, and some listeners suspected that he might prove to be the most musical Tristan since the legendary Lauritz Melchior, who virtually owned the role in the 1930s and '40s.

And now, at the age of 63, Domingo has proved it, with a new recording of "Tristan und Isolde" for EMI Classics (three CDs; $48.98). His performance is everything one could have hoped for -- ardent, lyrical, intelligent and astonishingly sweet-toned, with only a few effortful passages to remind the listener that Domingo has been before the public for more than 45 years. The love music is sung with melting tenderness and the protracted death scene, accompanied by ethereal and perfectly piped English horn, is both musically and dramatically enthralling. This "Tristan" will stand as one of Domingo's proudest legacies -- and a challenge to all who undertake the role in the future.

If Domingo realized that he couldn't sing the work in live performance, how did he manage to make such a fine recording? The answer is a simple one -- he took it on in pieces, recording only a fragment or two at any given time, thus preserving his voice, his stamina and his sanity. There is some precedent for this: Maria Callas remains perhaps the most vital Carmen on record (another EMI production), but she never sang the work live, nor was she tempted to.

Domingo is not the only reason to buy the recording, however. Nina Stemme is a radiant and impassioned heroine -- for once, we have an Isolde who sounds like a young Irish princess rather than a haughty, hooty Queen Victoria singing in German. Mihoko Fujimara makes an appropriately transfixed Brangane, while Rene Pape's King Marke is one of the finest and saddest on record. The casting is strong throughout, with rising stars Ian Bostridge and Rolando Villazon in small roles usually tossed off by second-raters. The chorus and orchestra of the Royal Opera House, Covent Garden, perform with ripe tonal opulence for conductor Antonio Pappano, who leads a brisk and straightforward (some may consider it featureless) performance.

EMI has announced that this will be the last complete opera recording the company will make. I am always suspicious of such grand pronouncements; a new owner or even a new CEO -- and they tend to come along pretty regularly in the music business -- may have other plans. Still, the cost of recording opera has become prohibitive and I can't imagine that this set came in at much less than $1 million, once all the studio and union expenses were paid. It stands hardly a chance of making back this sum -- complete Wagner operas do not sell as well as "The Three Tenors," even if they have one of the trio as the lead.

Half a century ago, EMI made what has long been considered the classic recording of "Tristan" -- a rapt performance featuring Kirsten Flagstad and Ludwig Suthaus, under the direction of Wilhelm Furtwangler. Aside from Furtwangler's conducting, which still seems the product of a magnificent and unparalleled delirium, I find the new recording even more satisfying. But fie on the EMI designers, who have given this "Tristan" a cover that would shame a Harlequin romance. Domingo -- and Wagner -- deserved better.

Placido Domingo has turned down the stage role in Wagner's demand- ing "Tristan und Isolde," but proves he's up to the task in the studio.