Wired has a series called “One Concept in 5 Levels of Difficulty”. Here is the one for harmony.
23-year-old musician, composer and multi-instrumentalist Jacob Collier explains the concept of harmony to 5 different people; a child, a teen, a college student, a professional, and jazz legend Herbie Hancock.
The video is 15 minutes long but worth watching till the end because 1) it’s interesting to see the notion of harmony explained at different levels and 2) Jacob Collier and Herbie Hancock do an amazing improv session at the end of the video.
Synthesist & Multimedia Artist