"It's hard for me to believe there is a mechanism in our bodies that could provide such a precise and long-term stable frequency reference on the order of an LC or crystal oscillator." - Dewster
A neat, one sentence summary of my ramblings! LOL ;-)
Which is why I hypothesise some external "clock".
As for A being 440 or 442 Hz - IF there is a "clock" then I am sure this is not at any integer multiple of these frequencies.. Whatever the "clock" is, the brain would probably 'only' be using this as a reference against which the "mental" frequencies are referenced - as in, these "frequencies" (which would not, most likely, appear anywhere in the brain as frequencies - but perhaps trigger a group of neurons or whatever to give the 'sensation' of a pitch) would require training / programming..
So (taking the above hypothesis) someone with PP who "trained" these neuron groups (or whatever) and memorised that the note exciting the network was A440, would be "fixed" on A440 .. The same person, if they trained on A=442, would establish that as the tone for A.. (someone training with a faulty set of intervals, where "A" was say 450 Hz, but believed this to be 440Hz, would find every piece played at concert pitch out of tune, I guess ;-)
I think the answer to " who tuned it to A440? " must be that the individual tuned it to that frequency, by listening to that frequency and being told somehow that the frequency they were listening to was 440Hz and was "A".
As to how anyone could accurately determine error (deviation) from their learned frequencies, to a degree that they could declare how many cents deviation there was - well, thats beyond me! A guess to perhaps roughly 10 cents - perhaps.. but one is talking about a massive leap from learning a set of 120 pitches, to either extrapolating accurately the deviation between two of these frequencies, or learning 12000 pitches spaced 1 cent apart if one is talking about identifying one cent errors. (Added: - It might be? that one does not learn all 120 pitches - that only 12 are required, with octaves being a seperate related mechanism, in which case only 1200 intervals would need to be learned to 'encode' with 1 cent resolution)
On the other hand - perhaps a group of neurons could give an analogue representation of "off pitch" intervals - if their rate of firing is proportional to the closeness of their programmed pitch, then if the interval fell between two learned notes, perhaps one gets equal firing rates from the two closest neurons, and this is interpreted as a 50 cent error - the degrees of firing of each neuron or whatever giving an accurate identification of degree of error .. (Added: In fact, some such mechanism must exist for the above hypothesis to have any validity - I can have mental pitch-bends - so whatever mechanism is producing these "pitches" must be "analogue" with a high resolution - Sitting here doing a mental pitch bend, I can hear no quantization or non-linearities or stepping or glitches at all .. The only mild sensation I have is that my vocal chords are slightly tensing as the pitch goes higher.. At frequencies I can sing, the pitch which comes out is the same as what I hear in my head - go higher, and there is a severe difference between what plays in my head and what I can manage to squeek)
My ideas / hypotheses above are just me thinking aloud - I REALLY dont have the faintest idea whether the above is at all feasible or whether someone with more knowledge of neurology would see it as complete BS! LOL ;-)
Like the light in my dreams, I now know it exists only in my cortex and not in the form of visible light - I also know that, even with the most sensitive equipment, one cannot find any audio frequencies in the brain corresponding to sounds one hears in your head.. I do not know what form these audio "signals" take in the brain, what encoding mechanism is employed, or any of that stuff.. I am reasonably sure that no one does yet .. But, advances in this field are enormous - IF one could find the brains "audio circuits" and decode these, the possibilities musically would be astounding (A cap I could put on my head, from which I could record the music I hear or create therein - the stuff of pure ecstatic fantasy! ;-) ...
But the first applications of such science / technology wont be used for that purpose - we all know how it will be used - it will be used to invade our last paramount privacy, the privacy of our conscious verbal thoughts..
(Added: I should just say that I am not at all sure that the "musical" audio mechanisms and the "verbal thought" mechanisms are directly related - I can "hear" music at the same "Soft, unfocussed" level as I "hear" my verbal thoughts - But when I am deeply into my head music, this music is far more "real" and "louder" than my normal verbal thought processes. I have no way of knowing if I am "normal" - but a lot of my thinking is verbal - often debating with myself, and its virtually "pitchless" - a lot of the time its probably uncertain whether its "brain audio" at all..But I can choose to crank it up, give it tonal qualities and expressiveness - and when singing in my head I can hear my voice and the music together - can change the lyrics or make them up as I go along - even sing in tongues if I want to, LOL ;-)
Fred.
