Major vs. minor
The real deciding difference between any major and minor key (like C Major vs. C minor) is the third degree, also known as the mediant, also known as the third note of the standard chord triad. For instance, the C Major scale triad is C - E - G, but the C minor triad is C - Eb - G. Wikipedia has a helpful graphic to demonstrate the differences: |
| C MAJOR |
 |
| c minor |
Three minor flavors
While there is only one major scale there are three possible minor scales:The natural minor scale looks like this:
i - iiº - III - iv - v - VI - VII
But apparently the natural minor produces a not entirely pleasing sound and so there are two variations:
Harmonic minor - the third is augmented and the seventh is minor and diminished.
i - iiº - III+ - iv - v - VI - ♮viiº
Melodic minor - (compared to natural minor) the second is no longer diminished, the third is augmented, the fourth has gone from minor to major, the sixth has gone from major to minor diminished and the seventh is minor diminished.
i - ii - III+ - IV - v - viº - ♮viiº
Equal temperament vs. just intonation
This was a real revelation, that thanks to the piano, just intonation could no longer be used to tune instruments, at least when the instruments were being played with piano accompaniment. However, apparently when string quartets are tuning without a piano, they are more likely to go with just intonation. Wikipedia has an entry.Diatonic vs. Chromatic
The reason for all this business with diminished and augmented intervals is due to the fact that Western music references two completely different systems - the old school 7-note diatonic system (think of it as only the white keys of a piano octave) and the new school 12-note chromatic system (the white keys and the black keys of a piano octave.) It took quite a bit of time for me to get it, but eventually I did.C Clef
