In a statement, the orchestra said that Barenboim is recovering in Berlin from herniated discs in his back and cervical myelopathy, a compression of a nerve in the spine that is sometimes a result of herniated discs. The latter condition can cause weakness in the hands and even difficulty walking, according to the web site of the Chicago Institute of Neurosurgery and Neuroresearch.

Barenboim is scheduled to lead the orchestra on September 17 and 18 and to appear as a pianist and conductor in late October. The CSO said it would make an announcement about his remaining performances in Chicago soon. He is also to give piano recitals in Seattle, San Francisco, and New York later this fall.

The CSO's gala performance tomorrow features violinist Nikolaj Znaider, playing Tchaikovsky's First Violin Concerto, and an appearance by the Lincoln Center Jazz Orchestra. On Saturday, September 11, the CSO will participate in the annual Marshall Field's Day of Music, playing Tchaikovsky, Stravinsky, and Ravel in a free performance. And on Sunday, September 12, and Tuesday, September 14, the orchestra performs Ravel, Stravinsky, and Szymanowski in its first subscription concerts of the year.