“Writing for the concert hall means waiting for a commission (probably for a concert opener, if it’s an orchestral gig; maybe an unusual chamber combination if you’re lucky), writing the piece, and much later on hearing it played two or three times as a novelty, or as a warm-up to masterpieces of the established canon. Your overture, no matter how good, probably won’t have a chance with audiences against the Mozart concerto that follows it and that Schubert/Brahms/Tchaikovsky symphony after intermission.” For the theatre, on the other hand…