The Australian comedy rock trio Axis of Awesome made an earth-shaking discovery: many if not most pop songs of the last 40 years use the same 4-chord progression:
I – V – vi – IV
Example: In the key of C major, this would be: C–G–Am–F. Whatever key you start in determines the mood of the song. Other than that, I know nothing about writing music, so I dare say no more. You can play around with the chords if you’re so inclined.
Anyway, it seems that if you write a song using these 4 chords, you will have a guaranteed hit, especially if you write a catchy melody to go over it. These four chords are also the reason why so many pop songs all sound the same.
All you have to remember is the melody and lyrics are the skin, but the chords are the bones. The bones may stand on their own with very little skin attached to them (generic commercial pop songs that are catchy but easily forgotten fall into the “bones without much skin” category), but a bunch of skin with no bones (bones could be other types of chord progressions) will collapse like Jello when it’s dropped on the floor.
We humans seem to be wired to especially favor the I-V-vi-IV sequence of chords, so if you want to become a filthy rich superstar, write a song using them. Conversely, if you want to be an artiste who turns their nose up at anything commercial or too popular, avoid them like the plague.
Here’s a hilarious (and surprisingly listenable!) video by Axxis of Awesome that proves almost every pop song written since forever uses the same four chords.