Many symphony orchestras have composers in residence, who write music and who work with the artistic staff to organize programs of contemporary music by other composers. Likewise, many theaters have playwrights in residence. Like their musical counterparts, these playwrights write plays and work with the theaters on educational programs and other projects. The Baltimore Symphony Orchestra has had its share of resident composers over the years, but it appears to be the first orchestra in the country to merge these two hallowed traditions by engaging a playwright in residence. Her name is Didi Balle, and she wrote and is directing a symphonic play that explores Tchaikovsky’s state of mind as he composed his Fifth Symphony. Marin Alsop will lead performances of Didi Balle’s new symphonic play, called Mad But for Music, this weekend. Didi Balle joins us in the studio.