Conductor emeritus Pierre Boulez, due to an undisclosed medical condition, has canceled his scheduled appearances in March with the Chicago Symphony Orchestra.

Replacing him will be Cristian Macelaru, associate conductor of the Philadelphia Orchestra, and Asher Fisch, principal guest conductor of the Seattle Opera.

Macelaru will lead the CSO on March 7, 9 and 12 in a slightly revised program, with Bartok's Divertimento for String Orchestra replacing Messiaen's "Chronochromie." The rest of the program remains the same.

Returning to Symphony Center for the first time since his CSO subscription concert debut in October 2010, Fisch will lead the CSO for three performances March 14-16, with no changes to the program.

For further details, call the CSO box office at (312) 294-3000.