Cellist Yo-Yo Ma and pianist Emanuel Ax have been performing together for 46 years — easily one of the longest and most distinguished collaborations in classical-music history. “It’s a very special part of my life, I have to say,” Ax said.

The two were most recently heard together in Orchestra Hall on Feb. 25, when they performed Brahms’ Piano Trios with noted violinist Leonidas Kavakos. The three first performed together at the Tanglewood Music Festival in Lenox, Mass., about five years ago. After some other concerts, the trio released a recording of the three piano trios by Johannes Brahms in September on the Sony Classical label. On Feb. 21, the three musicians embarked on their first tour together: a nine-concert itinerary that concluded March 4 in Disney Concert Hall in Los Angeles and included stops at Carnegie Hall in New York City.

Ax and Ma hadn’t worked with a violinist since celebrated violinist Isaac Stern died in 2001. The three famed musicians made many recordings together, including a well-regarded 1988 release featuring Shostakovich’s piano trios. Ax and Kavakos have known each other since the 1990s, when they met and later performed some recitals together.

The pianist then suggested to Ma that they team with Kavakos. “I thought they would really hit off,” Ax said of the two string players, “and I think they really did hit it off in about a half-hour. So, the whole project was for me was one big thrill.”