This is a relatively short post about an interesting article I found about the four chord song. This is the first part (the article comes in several parts, the others are linked in the post):

Four chord song article

It found that the majority of pop songs have similar chords, keys and chord progressions. They have also made a database of some 1300 pop songs to analyse. Interesting reading for music theorists, or people who are interested in writing popular music. Or people who dislike the lack of variation in popular music.

Also, Axis of Awesome!