Ideas That Changed Western Music

The BBC offers up this list of 8.
- Pythagoras creates the scale.
- Notation is developed.
- The piano enters the home.
- The first recording.
- The birth of public radio broadcasting.
- The first chart is published.
- The dawn of electronic music.
- The invention of the Walkman.
A Top 10 list needs, according to my calculations, 2 more. What would you add to the list?