In many instances, such a partnership would have dissolved after the pair achieved fame as soloists, their calendars increasingly filled with plum engagements and enticing new collaborations. But against the odds, Tetzlaff and Andsnes have continued performing together.
San Francisco on Tuesday. On Thursday, they will make their joint Walt Disney Concert Hall debut, though they have performed there regularly as soloists with the Los Angeles Philharmonic.
The recital, featuring music by Janácek, Brahms, Mozart and Schubert, will be their second as a duo in Los Angeles -- the first was in 1994, two years after they began working together. The repertory is noteworthy because though all celebrated musicians presumably choose their programs carefully, Tetzlaff, 42, and Andsnes, 38, are discriminating in an unusual way.
"When we get together, we want to play duo pieces," Andsnes said recently by telephone from his home in Bergen, Norway. "Christian has never been interested in a glamour role, doing virtuoso numbers with accompanists who sit in the back and keep the piano lid down."
Ara Guzelimian, who worked with both musicians as Carnegie Hall's artistic advisor from 1998 to 2006, called Tetzlaff and Andsnes a "duo of peers," noting that most of the pieces they perform "were conceived for a team of equals," then adding: "There is no question, or even any risk, of one being subservient to the other."
Describing them as exceptionally well matched, Guzelimian also lauded their ability to inspire each other, and even compared them to such legendary predecessors as Adolf Busch and Rudolf Serkin, and Arthur Grumiaux and Clara Haskil. "They're two of the most enormously appealing and deeply rewarding artists in the world today," he said, "so when you combine them, it's more than just the sum of the parts."
The two themselves appear to have only the highest regard for each other. "Let's make a checklist!" Tetzlaff said facetiously, speaking by telephone from the road, when asked to enumerate his collaborator's qualities at the keyboard. More seriously, he praised Andsnes' "beautiful sound" and offered this assessment: "I never feel any vanity in his playing, only sincerity. His interest is purely in great music and how we can make the deepest statement from it."
Andsnes praised something similar in Tetzlaff's music-making. "When he really hits it," the pianist said, "he gets straight to the truth of the music. He won't go for the big juicy sound just for the sake of it. There will have to be musical reasons for it. He will play with an ugly sound, if that's what's needed. He's not afraid of that."
Both musicians said that they liked each other from the time they met, after a recital Andsnes gave in Germany in 1990, but that forging a musical relationship took longer. "At first, we were rather surprised by what the other suggested," Tetzlaff recalled. "But over the years, we've come to understand each other's views and try to take from the other."
In addition, patience played a role in their success. "It took us a few years to adapt to each other's personalities and ways of playing," Andsnes said. "We had a couple of tours where I remember feeling a bit of frustration that we didn't really click, but after a year or two of working together, it was fine."
The pianist specifically remembered trouble with Mozart. "Christian would say my playing was too heavy, with not enough charm and lightness," he said. "But when I got closer to 30, this music opened up for me."
Such broadening has cut both ways, with Tetzlaff becoming a more expressive player over time thanks partly to Andsnes' influence. "He's still very concerned about the composer and the text," Andsnes said, "but within that, he is so much more personal and subjective."
Tetzlaff said his approach to performance was at one time "over-informed." "Leif Ove often confronted me about how to let go," the violinist said. "I'm a little less rigid than I was."
This cross-pollination has increased both artists' reper-tory. "When we met, Leif Ove had no interest in Bartók," said Tetzlaff, who champions the composer. "He said that the music gave him nothing, but now he plays Bartók often."
Andsnes also credited Tetzlaff with introducing him to the Ravel Sonata for Violin and Piano. "But I introduced him to Carl Nielsen's Sonata," he said, "so it's gone both ways."
Which isn't to say that after all these years the pair agree on everything. "Christian keeps telling me about the Berg Chamber Concerto," said Andsnes, "which is a piece I'm embarrassed to say I don't get -- well, I'm not so embarrassed to say it. But I'm disappointed to say it. I love Berg, and that piece would be perfect for us, but I just don't get it."
Tetzlaff must know the feeling, for recently Andsnes visited him at home outside Frankfurt, Germany, and played some Stravinsky. "He didn't like it," said Andsnes. "He said he doesn't like neo-Classical."
Tetzlaff is married, with three children, and Andsnes is single. But both musicians maintained that their long-standing, if inevitably infrequent, collaboration has created a bond unique to enduring relationships. "The wonderful thing about a long-term partnership," said Andsnes, "is that it gives you trust and freedom you don't get when you meet someone and play for the first time. In the beginning, we had to explain more. It's much easier now. We get it."
Tetzlaff went further, suggesting an almost telepathic connection. "We never look at each other onstage," he said. "We listen to each other, and we make decisions onstage, but we don't communicate. We have a blind understanding which we both like, and that's growing every year."
Others have noticed something similar. "They share an inner strength, which you can't shake," said cellist Jean-Guihen Queyras, who has performed chamber music at Carnegie Hall with both artists. "When the music starts, you can feel in both of them what we call in France la force tranquille, a quiet force, a strength that is serene."
True friendship has also contributed to their success, for they long have been more than just colleagues. "You spend many days and nights with a person when you tour together," Tetzlaff said, "so it's important to do it with someone you like."
Nor does it hurt to find shared enthusiasms beyond music. "Since the beginning, sushi has been a passion for us," said Andsnes. "We've found sushi restaurants in the smallest towns in Germany and on the outskirts of Toronto. There was a certain time when we couldn't eat anything but sushi. The tragic thing is that we haven't been able to tour together in Japan."
Their sushi fetish pales next to a darker predilection, which they enjoy mostly in secret. "We have one passion that I haven't mentioned," Andsnes acknowledged hesitantly, "and that's P.D.Q. Bach" -- the "forgotten" composer in the Bach family, invented by musical satirist Peter Schickele, and definitely an acquired taste. "It was Christian who taught me that! We just have to listen to that when I come to visit him, and we lie on the floor laughing. This time, his youngest son, Simon, who's 11, was with us. And I was very impressed that he got all the musical jokes in the 'Schleptet' and the 'Pervertimento.' So we were three of us laughing on the floor."
Tetzlaff, still the more buttoned-down of the two, may be mortified to find his peccadillo revealed. Yet isn't that always a danger with close friendships? Secrets are never safe. Still, taking a moment to review this relationship, the violinist seemed glad that a long-ago business decision had yielded such a fruitful partnership.
"Sometimes," he said, "an arranged marriage isn't the worst thing."