I've been trying to figure out exactly what notes are being played (piano part)for various chords and have come across some surprising things. For about 1/3 of the possible chord types, it seems that the root is not played by the piano (or guitar?). For example, displaying piano chords when playing a C6/9, the diagram shows R in blue and 2, 3 6 are indicated with black dots. On other chords, the root also gets a black dot. In other chords, the root is indicated in blue and also gets a black dot. Am I understanding this display correctly?