Two years before Walt Disney added a sound track to his third Mickey Mouse picture and "produced the first sound cartoon", Max Fleischer was producing "Car-Tunes" using the Phono-film system that later evolved into the modern movie-sound system. This series, including the 'bouncing ball' did not use the sophisticated playing-with-ink effects of the usual Ko-Ko cartoons that Fleischer was producing at the time, but they are definitely sound films - with an orchestra, people singing. They are worth a look for people with an interest in the history of film.