Major vs. minorThe 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:
Three minor flavorsWhile 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