There is a nice standup sketch from an Australian comedy group, the Axis of Evil, that most of the pop songs are using only four chords, https://www.youtube.com

There is a nice standup sketch from an Australian comedy group, the Axis of Evil, that most of the pop songs are using only four chords, https://www.youtube.com/watch?v=5pidokakU4I https://www.youtube.com/watch?v=5pidokakU4I