Similarly, you can see how it is that all the songs we have ever heard—and all those that will ever be created—could be made up of just twelve musical notes (ignoring octaves). Each note can go to another note, or to itself, or to a rest, and this yields twelve possibilities. But each of those possibilities yields twelve more. When you factor in rhythm—each note can take on one of many different note lengths—the number of possibilities grows very, very rapidly.
