Concept of music
Music has existed for many years. It's prehistoric to be precise, and has evolved into a very complicated construct. Even though it is complicated and could take you many years of education to master, music can be very formulaic. The fact that we can abstract the idea of music as a formula is what will allow us to make an algorithm to generate it.
Tempo
The first thing we need to understand is that a song will follow a tempo. The tempo of a song is the speed at which the song progresses. Every sound within the song falls within some range of the tempo by an equal measure. That measure is usually at pace with the tempo, at 1/4th, at 1/8th, or at 1/16th. The tempo as seen in the following figure:
This might sound strange if you have never heard it before. We can visualize each sound following a tempo as dots on a line or in a graph. The tempo can be seen as a vertical line that moves in the positive direction on the x axis. Each time the tempo line intersects...