Some kids are ready to play these chords before they read well. The letters-inside-the-note-heads are a lot like pictures - and a picture can be worth a thousand words! I have noticed a real difference
I did it for little guys and gals who are capable of playing more complicated music than they can read, and WANT TO. So why did I feel the need to make these 'dumbed-down' versions of the Key of _ sheets?