Reading music is not a simple skill by any means. Reading notation should ideally be taught entirely differently to singers than to instrumentalists. When instruments are concerned alternative notations should be introduced, like fingering charts and tabulatures so that the mechanical interface between sound and physical response is objectified.

Since the invention of the piano these distinctions have pretty much disappeared. People who play every instrument expect to read as if in terms of a keyboard. Why doesn't that work?

I am not a scientist, but rather an observant artist/teacher. I see that the ear works fast, very fast; and that the body responds slowly, very slowly. When the notation of sound is confused with physical instructions the perception of sound is slowed.

When children are taught to listen first their physical responses are dictated by what they hear. They don't produce sound, they respond to it. It takes longer to achieve this but the result is mastery, apparent already to the young learner. The love that accompanies this kind of learning is lifelong.