PLEASE don’t call Jonas Kaufmann “the German tenor”: it raises too many preconceptions about a restricted repertory a German tenor should address, and Mr. Kaufmann wants to sing it all. He seems to be doing just that with major opera companies from New York to Vienna, performing an impressive range of roles with a finely chiseled, deftly modulated lyric-dramatic voice capped by a secure, ringing top.


Such distinctive vocal quality would be enough to put any tenor’s career into orbit. But Mr. Kaufmann adds patrician musicianship to the package along with something even more uncommon: the perfect picture of what a romantic operatic hero should look like but seldom does.


Last fall Mr. Kaufmann starred in the Met’s production of Gounod’s “Faust,” and on Saturday he returns to sing Siegmund in “Die Walküre” as part of the company’s first full performances of Wagner’s “Ring” cycle in Robert Lepage’s new production. Few tenor roles could be more dissimilar, stylistically or vocally, and these two present exactly the sort of challenge Mr. Kaufmann seems to relish.


“Have many other tenors ever sung Faust and Siegmund back to back?” he asked, more genuinely curious than boastful, when interviewed the day after the Gounod opera opened in November.


Long pause. Well, the fabled Polish tenor Jean de Reszke did, but that was 125 years ago, and no one now knows what he sounded like. (The only surviving evidence of his voice, faint snippets caught live on Mapleson cylinders in 1901, really doesn’t count.) Plácido Domingo has also sung both roles, but at the poles of a long career. No matter. Mr. Kaufmann’s vocal versatility and flexibility at 42 are rare qualities at any time, especially in these days of singer specialization and compartmentalization.


“And yet only a few generations ago,” Mr. Kaufmann pointed out, “nearly all singers moved easily from one style to another. Just the other day we were listening to recordings of the wonderful American mezzo-soprano Risë Stevens singing Wagner’s Fricka in 1940, Bizet’s Carmen in 1950 and Mozart’s Cherubino in 1955, all of it fantastic. It’s difficult now to convince theaters to accept that sort of versatility. We’re all in danger of being typecast, and it took me a while to get past that sort of thinking. Early in my career a manager actually asked me, ‘What’s a German guy like you doing, singing Italian opera?’


“On the other hand, if you have a success in a certain part, then every theater wants you to sing the same role over and over. I could spend the next five years performing nothing but Siegmund if I accepted all the offers that came my way after I first sang the role here at the Met last year. Luckily I’m at a sweet point in my career, when I can negotiate. O.K., I’ll sing the German role for you this time, but when I return, I’d really like to do this or that Italian part and maybe even a French opera. Now I can bargain, but it was a real struggle before I reached that point.”


The struggle began with Mr. Kaufmann’s first operatic engagement, in 1994 at the modest State Theater in Saarbrücken, after he had completed a full five-year course of study at the Academy of Music and Theater in Munich.


“Back then I kept my voice sounding light and white, which was then felt to be proper for a singer of my training and background. It was a bright, airy, flexible type of German tenor in the Peter Schreier mold, suitable for Mozart or Rossini. Everyone encouraged me that this was the best way to go, because I was young and just getting started.


“But right away in Saarbrücken, where I had to sing and learn a lot of new repertory in a very short time, I started to have terrible technical difficulties. Instead of giving my voice the full body support and muscular control that came naturally to me, I was squeezing out the sound that I thought I wanted to hear. Thank God, I soon found another teacher, who told me I was doing something completely wrong.”