Ear training teachers everywhere, take heart. For it was one of your own, Guido of Arezzo, an ear training teacher from the turn of the first millennium (A.D.) who produced what Taruskin calls “perhaps the greatest [breakthrough] in the history of the literate tradition of music in the West” (I, 101): the musical staff with “key” lines, which we now know as clefs. Not to mention that other little device, solmization syllables.
How did these breakthroughs come about? Guido was just trying to be a better teacher. I wonder what breakthroughs we can come up with by aiming for the same goal.