Ed Foote schreef:
 
> [...]  The sensation of leaving a pure key, going into something more
> "active", often feels like the floor dropping,  and things getting
> spread out.
> I have often thought of it as leaving the firmer foundation.
 
This seems to me like the third dimension.  The second would be
intervals, analogous to distances between tones.  A single dimension
would be a single tone - I suppose a sine wave, since harmonics already
imply intervals.
 
I'm not quite sure where this is getting us....
 
Dale