I'm not sure what Carol C means by this hearing the music in the head which she can't do. Do most people actually hear music in their head ?

Whistling or singing is the type of music making that seems most relevant here, because when we are doing that there are no clues from fingers and frets and so forth - and yet most of us seem able to whistle or sing a tune. Regardless of whether we can read music or not. (And I can't.)

When I whistle I know when the note I make is the note I want, and I can normally move up or down to the next note I want (though I've no idea how I do that)- but hearing the note in the head? No way. Sensing the interval between the notes, maybe that's a better way of describing what happens.