If I understand it correctly, the key to this method is to teach children to recognize chords first and then the notes in them. They practice by associating a different colored flag with each chord.
Had to look up the technique, Eguchi method, and it uses color rather than complicated musical notation to associate with each key. Interesting how those who have synesthesia naturally have this same color, key association.
I have a step in my fashion work where I pause and consider what the colors I’m selecting will look and feel like to a normal person. Converting back and forth between [optimistic-seaglass-springtime] and “teal” isn’t very accurate, but I’m certainly accustomed to it. I’m going to try this technique soon now that I know about it; as I’m already color sensitive to pitch, I suspect the value will be in training that sensitivity rather than memorizing their hues.