diagram of the universe that is music.  Also known as the cycle of 4ths.  It's a circle that can help you determine the Major and minor key signatures and see how they relate to each other. Modal Scales : Ionian/Dorian/Phrygian/Lydian/Mixolydian/Aeolian/Locrian….. all the same thing.  Ex: CDEFGABC, DEFGABCD, EFGABCDE, FGABCDEF, GABCDEFG, ABCDEFGA, BCDEFGAB.