Leonard Bernstein - The Unanswered Question, Musical Phonology (1973)

For those wishing to dive even deeper into the understanding of music, check out this monumental dialogue on music by the great Leonard Bernstein. It takes a while for it to get rolling (at 27 minutes in he gets to the meat of the lecture), but he brilliantly lays out why the overtone series (also known as partials and harmonic series), how chords are built and why we have the 12 tones we have in music.

YouTube:
http://www.youtube.com/watch?v=U3HLqCHO08s&feature=relmfu