A few months ago, I was challenged to improvise a piece of music with an orchestra, with no plan, no sheet music, no rehearsal, and no prior discussion. Here's what happened.

NSO Artistic Advisor Ben Folds composes a piece live with the National Symphony Orchestra and conductor Edwin Outwater during Sound Health in Concert: Music and the Mind, an initiative spearheaded by Artistic Advisor At Large, Renée Fleming, presented by...