Celebrity conductor Michael Tilson Thomas said on Friday he would be retiring from performances for the next few months as he recovers from surgery to treat a brain tumor.

Thomas, 76, the former musical director of the San Francisco Symphony, said in a statement he would take a hiatus until October while undergoing treatment. He said doctors recently discovered the tumor and advised him to have surgery immediately. He described the operation, which took place at the University of California at San Francisco Medical Center, as a success.

“I deeply regret that I missed projects that I had high expectations for,” Thomas said in the statement. “I can’t wait to see everyone again in November.

Thomas, a prominent figure in the music industry known by the nickname MTT, stepped down as Music Director of the San Francisco Symphony last year. He had held this position since 1995 and was widely recognized for turning the ensemble into one of the best in the country and championing the works of modern American composers.

Thomas said in the statement he was canceling his participation in a star-studded concert with the National Symphony Orchestra in September to celebrate the Kennedy Center’s 50th anniversary, as well as appearances with the New World Symphony, a training orchestra for young artists at Miami. that he helped to found; the Indianapolis Symphony Orchestra, where he will conduct his “Agnegram” alongside works by Beethoven and Copland; and the Chicago Symphony Orchestra.