Years ago I watched a British documentary called Howard Goodall's Big Bangs. It's well worth watching. It explains how music theory developed from Pythagoras's

Years ago I watched a British documentary called Howard Goodall's Big Bangs. It's well worth watching. It explains how music theory developed from Pythagoras's (matching the 12 keys on the piano). It's an interesting exercise to "prove" these 12 steps based on this simple ratio. What came much later was equal temperament. The 12 steps don't match up exactly. Equal temperament changes the notes slightly by changing the ratio slightly (to factors of the 12th root of 2). I believe it was Bach who first discovered this. Not all cultures use equal temperament but it is overwhelmingly dominant in the West. The series also explains chords, keys and so on. For someone like me who is more mathematically inclined it was fascinating. Give it a look if you can. Oh also it wasn't the BBC as you might expect. It was Channel 4.