I'll tell you what I've learned, and then my sources. The raw
material of music, like geometry, is an expression of number. By 'raw
material,' I mean 1) the harmonic series (fundamental, fundX2=octave,
fund x 3 = 5th, fund x 5 = major third, etc, and 2) the simple triads
and seventh chords of functional harmoncy which are based on the
simple ratios of the harmonic series (eg, major triad is 5/4, 6/5, and
3/2; dom 7th is 5/4, 7/5, and 7/4, etc.