The Exchange and the 24 Hour Company are to announce on Monday that Ben Folds will write a 15-minute musical that is to be cast, written, rehearsed and performed in a single day as part of the fifth production of “The 24-Hour Musicals.” The process will begin the evening of April 28 and continue around the clock until a total of four planned musicals are performed at the Gramercy Theater at 8 p.m. on April 29. Other participants have yet to be announced. Tickets are scheduled to go on sale in March, and proceeds will benefit the nonprofit Orchard Project, which helps develop new theater work. Information is at 24hourplays.com.