>Now, with synthesizers, we could make keyboard instruments that
>adjust their tuning on the fly so that all chords are true.
Yes and no. Much modern harmony makes use of the ambiguity inherent to
12-tone scale. A diminished seventh used for a modulation would often have
to have a different tuning to match the chord before it than it would to
match the one following. Also, if the retuning is "on the fly", in the sense
of not preprogrammed, there is the problem of chords which are ambiguous
until the next chord is played, but which must have been a certain chord once
you've heard the next. The retuning would have to be done in advance.
Wendy Carlos has some interesting pieces on "Beauty In the Beast" using
alternative tuning methods, including one that uses retuning while playing to
achieve better chords. The chords sound very nice but the effect of the
notes changing pitch disconcerts me.