In the tenth century, Guido d’ Arezzo was having trouble teaching monks their Gregorian chants.
So he replaced the A, B, C music scale with sound symbols which we now know as Do, Re, Mi.
He could point to a spot where he had written them on his hand and the monks would know exactly which note to sing.
These hand symbols evolved into the phonetic music scale and gave Maria a song to sing in The Sound of Music.
