I think Milt Kahl's point was that if one is going to do something, it's worth devoting one's full attention to it. It does not just apply to drawing, but to any activity.

When I read that, with a couple of exceptions, I stopped listening to music when I drew and I noticed a big improvement in my drawing. I do sometimes listen to music when I draw when I'm making drawings that are meant to go with that particular music, or occasionally when just doodling when listening to the radio as a way of just doing _anything_ when things have been difficult. These are just exceptions, though.

On another board, I read something about things guitarists can do when a guitar isn't at hand; visualization and things with your fingers. People can do whatever they want, but my personal opinion is that that sort of a thing is a waste of time. When I draw I draw, and when I practice the guitar, I practice the guitar, and when I makes tea, I makes tea, and when I makes water, I makes water (just not in the same pot!).