Conductor Seiji Ozawa, who recently underwent treatment for cancer of the esophagus, will sharply reduce his concert performance at an annual music festival in Matsumoto, Nagano Prefecture, due to back pains he has long been suffering from, festival organizers said Thursday.

While Ozawa, 74, has been making satisfactory progress since completing cancer therapy, his backache has gotten worse as he lost some muscles as a result of the treatment and his doctor has advised him not to conduct for long hours, organizers of the Saito Kinen Festival said.

Ozawa will be replaced by Tatsuya Shimono, 40, for eight programs, including "November Steps" by Toru Takemitsu, on four orchestra performances from Sept. 5 to 9.