When Emanuel Ax and Yo-Yo Ma perform together in a Brahms Project recital Feb. 21, it will mark the latest collaboration among two friends who first met while students at Juilliard in the early ’70s.

“Being on stage with him is always a great thrill for me,” says Ax (pictured above). “He is special in every way, and the way he plays is exactly who he is: charismatic, warm and generous.”

As Ma (inset photo, at right) told the Los Angeles Times last month, “Manny was obviously smart and also nice and told a lot of jokes — those were some of my first impressions. And guess what? That’s still my impression.”

They have performed together at innumerable concerts and on some 34 albums across an astonishing range of composers — including Brahms. This season, Ax is celebrating that composer with a series of chamber concerts titled the Brahms Project. Sponsored by the Chicago Symphony Orchestra Association’s Symphony Center Presents, the Los Angeles Philharmonic, Carnegie Hall and Cal Performances at the University of California at Berkeley, the project commissioned contemporary composers to write pieces that would resonate with essential chamber works by Brahms. In addition to two Brahms cello sonatas and a Brahms piano and cello work, the SCP concert features Hommage à Brahms by Australian composer Brett Dean.

This concert follows the Brahms Project performance in January featuring Ax and mezzo-soprano Anne Sofie von Otter. The series concludes May 18 with a solo piano recital featuring Ax in Brahms works and Bolts of Loving Thunder by New York City-based composer Missy Mazzoli. “[The Brahms Project] is a wonderful program that allows listeners to again go deeper into Brahms and also understand how his music influences some of today’s great composers,” Ax says.

Brahms remains a polestar for Ax, in music and life. “Just like many people, I have a special love for his music,” Ax says. “And I also have great sympathy for the person he was — so generous to others financially and anonymously. He helped fellow composers as well as other people he admired. The Schumanns. He admired Robert and was in love with [his wife] Clara. The situation caused him a great deal of sadness, despite his great successes. So some of his music — beautiful as it is — has a lot of sadness in it. Hope and happiness do not come to mind. But it is still amazingly beautiful and exciting, with a sad backstory.”

After so many years of playing with Ma, Ax confirms that the cellist “is in my consciousness. He is extraordinary in the way he listens and reacts to what is going on around him and contributes his unique musicianship. He expresses the special privilege of having the job of being a musician. We all try to do it. But he’s really good at it.”

For his part, Ma has said that he and Ax “have a shorthand. We know each other’s timing really well — we kind of feel it. Manny and I go through different phases of life, and we learn things and get back together, share what we’ve learned, and then go back off again. It’s a very, very special relationship.”

Ronald Litke is a Chicago writer whose work has appeared in the New York Times and on the BBC, among others, and is a content contributor for Chicago-based Rivet News Radio.