[alexophile]

People sometimes guffaw at this, but I can't recommend Donald Duck in Mathemagic Land enough: http://www.youtube.com/watch?v=iEVGQKwKeCc They skip over several centuries of shifting and tweaking between the triad and the modern (western) major scale, but it's a great visual answer at least to your second question.

[Jun8]

Funtastic! On behalf of HN, I award you, sir, with the best link posting of the day award!

[ghotli]

I recently went on a crusade to find this and show it to my children. I view it as a turning point in my development and one that influenced my life's path a great deal.