The bouncing ball is a device used in films to visually indicate the rhythm of a song, helping audiences to sing along with live or prerecorded music. As the song's lyrics are displayed on the screen (usually one line at a time), an animated ball bounces across the top of the words, landing on each syllable when it is to be sung.
The bouncing ball has been used in many films and television programs over the years. High-profile modern use of the bouncing ball include its most prominent and extensive use on television was in Mitch Miller's Sing Along with Mitch program (1961–1964).
Well that takes care of a couple more - Do you remember any of these? I think I watched way too much TV as a youngster. More answers soon.