I have the beginnings of a tool to convert humming to musical notes. A simple music composition system with speech driven and/or simple keyboard commands would be very popular. You hum a bit of a tune, choose an instrument to play it, loop that, and it becomes the background for the next track. Then you hum something over that, choose an instrument and you’ve on your way to a brilliant composition.
Pete thinks the Jokosher project might be relevant.