Richard --

That's a very good breakdown of the various steps in the process for people who are neurotypical, except that I am not neurotypical. I was born with a funky cerebellum; according to current medical theories about "my type" of cerebral palsy, my cerebellum is missing bits of "white matter" around its neurons (think of it as the insulation around phone wires; if that insulation is missing or patchy, you'll hear more static than conversation from the person on the other end of the line, even if both of you can hear and speak perfectly).

This is how it works (or not) in me:

1. Ears detect sound. [success]

2.a Ears send signal to the temporal lobe. [success]

2.b Temporal lobe receives signal [success]

2.c Temporal lobe sends signal to Frontal Lobe and the cerebellum [success]

3.a The Frontal Cortex receives signals from the temporal lobe, and successfully decodes them as a rhythm. [success]

3.b The Cerebellum receives an incomplete signal from the temporal lobe, and loses the timing aspect of the rhythm [failure]

4.a Frontal Cortex decides to make a go of it anyway, and sends signals to both the muscles, and the cerebellum, to coordinate the muscles [success]

4.b The Cerebellum receives an incomplete signal from the Frontal Cortex, and loses track of the coordination [failure]

...And we never get around to the #5 you wrote. So instead, we get:

5. Frontal Lobe decides: Screw it! I'll stick to writing lyrics, and ask people with cerebellums that know their axons from a hole in the ground to double-check my scansion (and cook up a tasty stew or something, for the musicians, instead -- you like garlic?).

I'd always known there was a breakdown at 4.b... and that's where I thought the main glitch was. But when I eliminated those gross motor skills from the equation, I discovered the core of the problem was all the way back at 3.b. And I thought that was fascinating. And I might have learned this fact about myself a heck of a lot sooner if the doctors and therapists who worked with me since I was two had considered music a crucial skill.

And this lack of insulation in my cerebellum has been there since I was born, and practicing over and over won't grow me any new insulation, either. That's the definition of "cerebral palsy."