Hi.
If one is actually playing *music* when playing Bach on the pipe organ, than one is indeed thinking deeply about all the parts at once, how they intertwine and what they might "mean", both separately and in combination. Same when one is improvising in counterpoint. Same, if one is sight reading and trying to have real music flow out. I'm afraid that one really does think about these in parallel combination (as I said, very much like watching a theatrical production with multiple actors on the stage, but sonically). It's learnable, and lots of people have learned how. I believe that many advanced thinking "skills" have quite a bit in common with all this. You can learn how to have multiple "thinkers" working on different aspects of ideas, all together.
Isn't a theatrical production an account of a long exchange of messages which are answered? If so, how many simultaneous "processes" would a typical theatrical production have? Same question for sitcoms? I suspect the answer, at least for sitcoms, is never greater than 2. Evidently there could be many more processes than 2 as long as they don't execute at the same time. I don't think there would be more than 5 anyway (lower bound of 7±2), otherwise the authors would be reducing their audience.
When I was learning how to type I noticed that I'd think what to say, spell it out, then that stuff would be mapped into a queue of things to write... think faster than you type and you lost track of what you wanted to write. Think slower than you type and your hands will wait until the queue fills up. When the queue is full enough, a daemon (now I can say I have a daemon for this, after ~20 years of typing on a qwerty keyboard) comes around and maps each letter into something one of my fingers would have to do. Usually, there's some sort of digram recognition as well, like "ll", shift+' -> " and so on.
I wonder if this is how people read music when they are interpreting it... maybe they develop multiline decoders for each line of the pentagram, which are put into a queue, which then are processed by the daemon, which puts all that stuff in another queue, which is sent using an internal clock down to the hands and feet. Or maybe it's just a linear decoder which reads each beat of the pentagram top down?...
How many fingers are usually used simultaneously to depress keys when playing say the piano? When playing the organ with pedals and manuals, I'd be inclined to suspect that the magic number is ~7... two feet, 5 fingers. Therefore, a key to execution difficulty is the max number of simultaneous keystrokes (if you will). Music could be even scored for difficulty like that... choose a suitable number x>1. Then the difficulty involved in playing something without error would be:
Sum{0<=i<=12} n(i)x^i
where n(x) = number of times in the score in which you have to make x depressions. Thus players could be scored. Of course there are other factors such as playing speed etc...
Andres.