The next task is to spell out some very common progressions, look at how the minor scale differs from the major scale, and once and for all explain exactly why V pulls to the I chord so heavily each time it comes around. Now you will look at the norms and figure out creative ways to go beyond them. Chord progressions and harmony comprise a vast subject, and you have only started to scratch the surface. Other chords and scales exist and yield great possibilities for analysis and composition.