Pierre-Laurent Aimard, down the rabbit hole with Bach

J.S. Bach has become early-career music: Wait too long, and you might not have time to give this composer - whose work is the foundation of so much of what's heard today - his full due.

That's why Pierre-Laurent Aimard could have missed the boat on Bach, having played the music when young. He then walked away from it pleasantly overwhelmed, but ultimately took a seven-month sabbatical at the Berlin Institute for Advanced Study before going public this year with The Well-Tempered Clavier, Book I. The result: a Deutsche Grammophon recording and now a tour that arrives here Tuesday, courtesy of the Philadelphia Chamber Music Society.

Originally, the Lyon-born pianist, 57, went so far down the rabbit hole with Bach that he insisted on playing Book I's 48 preludes and fugues - which weren't even written to be played in concert and ostensibly present themselves as something of a keyboard instruction manuel - sans intermission.

"I wanted to experience this big flow. But then, after playing this for friends, I realized it was too much for the listener, too much for the player," Aimard said on the phone the other day, explaining why he changed his mind. "The brain works so hard, you need a moment for relaxing."

It's a singular moment for a pianist as well known as Aimard. Taking time off isn't unusual for a midcareer pianist; doing so to study a single work - with time to explore all sorts of music and talk with all manner of artists - is quite another. He also sifted through Bach's preludes and fugues to find out what previous incarnations the music had before the composer sat down to explore what was, in the 18th century, a recently instituted standard of tuning that allowed new freedom to change keys however composers wanted.

Interestingly, the Bach performers he most connects with aren't even instrumentalists, but conductors of Bach's choral works such as Philippe Herreweghe, Nikolaus Harnoncourt, and John Eliot Gardiner. Such a rogue mentality might be expected from Aimard, who has devoted his career to modern music; his breakthrough recording was 2000's Messiaen's Vingt Regards sur l'Enfant Jesus. More recently, he has premiered concertos by such fearsomely complex modern composers as Harrison Birtwistle and Helmut Lachenmann.

Here's the best part: Aimard disdains that other great Bach maverick, Glenn Gould. "He was a strong personality, obviously, something of a genius, but his eccentricity was so big that it disturbed the listening too much. To play Bach, you don't need a star whose ego will decide too many things . . . and pervert the musical message."

Not that Aimard is out to be purposefully different: "I'm interested in trying to be true. I'm not arrogant. I just try. We always fail somewhere. Only Bach could be true with his own music."

One beauty of Bach is that so much leeway is possible; endless viewpoints are accommodated. Aimard's first return to Bach in 2008 was with the most open-ended work of all - the late-period Art of the Fugue, which seems not to be written for any particular instrument. The much-earlier Well-Tempered Clavier, though, comes with the old harpsichord vs. piano question. And to what extent is the music some post-Pythagorean exploration of what's possible in music? How much is more personal artistic expression?

Aimard jokes about how pianists who play Bach are sometimes regarded as criminals for not using the harpsichords Bach knew. Ultimately, he decided on piano but used in a rhetorically appropriate way, noting that Bach's "creativity was beyond any border. His own instruments were never enough for him. And he always had a very open mind."

As for the music's content, both answers are right. Bach was teaching himself as well as the outside world about the physics of music, but was always an artist, in Aimard's words, "with all the possible palette of feelings - a fresh, genuine explosion of glory or the most painful universal lament."

Nonetheless, some critics reviewing Aimard's Bach hear much more of the former than the latter. The Guardian called his viewpoint "remorselessly technical." But years of playing modern music for small, uncomprehending, or hostile audiences has hardened him to audience and critical reactions.

"There are always people who don't like what I do. I don't go onstage to be liked by a lot of people," he says. "If there are some people who appreciate what I do, I'm happy. If not appreciated, I won't change my mind for that."

Being guided by audiences, he says, opens the door to marketing-dictated art that he sees all around him: "We live in a world that's basically wrong. That's why I will go with music that will have a very small audience. If I believe in it, it's the right."

Yet if the world is so wrong, why is Aimard so successful? He has mostly blue-chip concerts. Also, Deutsche Grammophon has allowed him so much flexibility that, at one point, he released a CD single with two short pieces by the American modernist Elliott Carter.

"I think that I was born at the right moment for what I want to do," he said. "And I've been very lucky to meet a lot of people who wanted to share this adventure."

And just because he is playing the first book of Bach's Well-Tempered Clavier doesn't necessarily mean he's moving on to the second book: "I don't want to be a supermarket of music. If you want to play everything, you play nothing."

Pierre-Laurent Aimard

8 p.m. Tuesday at the Kimmel Center's Perelman Theater.

Tickets: $24.

Information: 215-569-8080 or www.pcmsconcerts.org.EndText