Does the drop in pitch result from the denser fluidic properties of the air stream when under higher pressure?
The discussion on the 'bluesbox&trade' reveals that there is more to do with harmonica reeds 'bending' in pitch than just air pressure changes. It has more to do with impedence matching of the 'exciter' (the reed) with the air passage, and the resultant effect when there is a change in the relationship.
Yes, there is a distinct difference between the concepts of the 'relative pitch' effect of setting a 'tuning standard' for the whole instrument relative to other instruments, and having individual "Reed Ranks" within an instrument tuned to slightly different pitches for the 'same note" - I discuss the latter in considerable detail with regard to 'tremolo' and 'phasing' effects in the Accordion 4RM thread referred to earlier. I would appreciate any useful comments on that material in case I have made errors.
The higher string tension as used by Paganini affects the projection of the sound. So tuning a 12 string two semitones lower to 'D' and capoing up to play 'normally' in 'E' will thus give a slightly mellower sound? (I am a non guitarist!)
Also, by taking this idea further, - a pianoforte with higher string tension will thus be brighter at the same pitch. The invention of the steel framed piano, especially uprights seems to bear this out - does this mean that the percentage of the higher overtones present in the sound envelope increases?