Sean Breheny wrote:

>I think the current scale is the equal-tempered scale (which existed at
>least as early as J. S. Bach, because he used it to write the Well-Tempered
>Clavier - a set of pieces written in each key allowed under the scale)
>transposed slightly upward, but I don't know exactly who agreed upon it.
Mostly right, I think. I looked into this a little bit several years ago
to help me write an essay for the magazine I used to work on, and here's
how I understand it:

Yes, the current scale is the equal tempered scale (which just means that
the intervals between all adjacent notes are equal). Originally the notes
were based on the "ideal" frequencies exhibited by vibrating strings or
columns of air - it came from physics - but the modern scale has been
shifted around slightly to even up the intervals. In fact, it was during
Bach's time that the changeover occurred: Bach was one of the main
proponents of using equal temperament, but many people at the time
thought it was an abomination. In fact, Bach wrote the Well-Tempered
Clavier in part to demonstrate how useful equal temperament could be: you
can play a piece in any key on the same instrument without re-tuning. In
"true" temperament,  instruments had to be tuned to a particular key, so
you coouldn't, for instance, change keys in the middle of a piece.

You can find avante garde music today that uses "true" temperament, I've
never heard it but people tell me the difference is definitely
noticeable, and kinda strange :-).

(If you're interested, the essay - which ended up having very little to
do with music - is at:
http://www.mactech.com/articles/develop/issue_20/109-111_Vet_Neophyte_8_31.
html)

Dave Johnson