Take “Peter and the Wolf,” for example. Sergei Prokofiev wrote this concise symphony in 1936 after an invitation from the Central Children’s Theatre to write a score to cultivate a child’s musical tastes and spark her interest in the sonic possibilities of an orchestra. It was a slight commission, and he was already a well-known composer; still, Prokofiev worked furiously over two weeks to write both a story and the music that would propel it. He had two young kids at the time and realized that an adventure story, better yet one with a bit of danger, would hold a child’s attention; meanwhile, the music could get on with its hidden agenda.