Yo-Yo Ma does not believe in making things easy on himself.
It was not enough for him that his sold-out concerts this week with David Zinman and the Baltimore Symphony Orchestra would feature him in three concertos. The great cellist, perhaps the most popular string player in the world, is scheduled to play Bloch's "Schelomo," the late Stephen Albert's Cello Concerto and Bela Bartok's Concerto for Viola in a transcription for cello.
But when Ma walks on stage at Joseph Meyerhoff Symphony Hall to play the Bartok, a lot of people are going to gape.
Ma will not be carrying his 250-year-old Stradivarius. He will be carrying what looks like a miniature cello that suffered an accident at the dry cleaner's. It will be, in fact, a huge viola -- 20 inches long in the body instead of 16 inches and with an end pin in it so that it can be planted, cello-like, on the floor -- that was made recently to specifications designed only 30 years ago.
The Bartok Viola Concerto exists in a cello transcription by the composer Tibor Serly, a friend of Bartok who completed the Viola Concerto after the composer died and later transcribed it so that it could be played on the cello. But after learning to play Serly's transcription, Ma decided that he was not happy with the way it sounded.
"The cello is too cultured," Ma says. "The Bartok's a tragic work, and it needs the viola's suffocating cry."
Although Ma cannot play the viola -- at least not the way violists do -- he possessed an instrument called a vertical viola or an alto violin that was designed in 1962 by physicist and instrument maker Carleen Hutchins as part of a new family of stringed instruments. Too long for most people to play under the chin, it can be played cello fashion on a long pin. And it had the sound that Ma thought he wanted.
"Instead of playing it in the Serly version, I said, why not on something that approximates the viola and see if it can work," Ma says. "It's part of being a musician just to explore. Some people do it by inventing new instruments and new material. I'm trying to figure out if it's possible to do that by finding another expressive medium.
"Many of the works that cellists play today, such as Schubert's 'Arpeggione' Sonata and the Bach Sixth Cello Suite, were not written for the cello, but for instruments that became extinct. People have always tried to do things better.
"In the same way that [Baltimore instrument maker] Jim [Cox] is trying to figure out better ways to build old instruments, Hutchins was trying figure out a better way to build new ones. Are we mired in so much tradition that you can't get out and do new things? These are questions today that we have to keep asking."
Those are questions that Ma has not refrained from asking ever since -- several years ago -- he decided that he had an obligation to music's future to try to widen the cello's repertory. He's been doing it by helping to create new works, such as the Albert Concerto, which the BSO commissioned for him three years ago, and by experimenting with electronic instruments such as the computerized "hypercello" that Massachusetts Institute of Technology composer Todd Machover designed for him a few years ago. (Machover wrote a concerto for the instrument that Ma has performed with the Boston Symphony.)
In fact, depending on whom you speak to, Ma's become the Ancient Mariner or the Don Quixote of the cello world, pigeon-holing composers and conductors to try new things and relentlessly questing for fresh challenges.
"He needs risks to keep himself alive," says BSO music director Zinman of his longtime friend. "He doesn't want to be a circus horse who goes through his paces. He's been telling composers, 'Write whatever you can -- as high as possible or as hard as possible -- and I'll find a way to play it.' "
"I don't know whether it will be a success or a failure," Zinman says of Ma's attempts to play the Bartok on the vertical viola. "I just know that it will be done with his heart and soul."
Ma first tried out the Bartok on the vertical viola in concerts in January with the Toronto Symphony.
"I had to learn to play it as a different instrument," Ma says. "Doing it and doing it well are two different things."
Ma first had to learn to read the notes in the viola's alto clef instead of the cello's bass, treble and tenor clefs. Harder for him, he says, was that the vertical viola's shorter body made the fingering different and the instrument harder to hold.
"It was not easy for him because it's a big adjustment -- the fingerings are different and much smaller than the cello's," says Steven Dann, principal violist of the Toronto Symphony. "And he had to come to terms with the way the viola speaks -- you can't push it the way you can a cello.
"Plus, the sound [of the vertical viola] is like a gamba's -- reedier, like an early-music instrument -- rather than an ordinary viola's. But Yo-Yo's a great artist, and he did a wonderful job."
Ma says that the jury's still out on his experiment with the viola, but adds that the final result may not matter.
"When you play a new instrument, you develop a relationship with different sound expectations and acquire different skills that you bring back to the old instrument that you play," he says. "It's always a learning experience."
"He's like the people who want to climb Mount Everest because it's there," says Zinman, who will record the Bartok work with Ma on the vertical viola (as well as the Albert and Bloch with the cellist on his accustomed instrument) for Sony Classics after the concerts are over.
"Everyone," adds Zinman, "me included, will be curious about what happens."