Q: why is the circle of 5ths important? why not the circle of 3rds?
A: there are circles of thirds. there's a circle of major 3rds, which is 4 different but identical circles, containing 3 notes each. then there is the circle of minor thirds, which is 3 different identical circles, containing 4 notes each. these are also known as 'diminished' or 'augmented' chords. both usually result in a dizzy or disoriented feeling when used exclusively