Temperaments

[Evoniuk, Gary E]

< Or why not D? (Actually, Beethoven's 9th IS in D.) >
I hope you will excuse a few comments by a lurking, non-tech orchestral
musician who also happens to be interested in pianos, key colors and
temperaments:
I tend to agree with arguments voiced by Ed Foote on the importance of tone
color lent by unequal temperaments in the key choice of many composers BUT
the contribution of orchestral color as it relates to key should not be
overlooked.  Examples (I'm a timpanist, so please excuse some of the
"timpanocentric" examples):
Pre-20th century composers wishing to include a timpani part would commonly
avoid the tonic keys of F#, G, G# and A unless they were willing to write
the timpani in 5ths (upper note as the dominant) rather than 4ths (lower
note as the dominant).  Corollary: There are no timpani parts for Mozart
works in the keys of G and A.
In the aforementioned example of Beethoven's 9th, it is conceivable that the
limitations of timpani of his day influenced his selection of key choice.
The scherzo contains the famously innovative writing of timpani in octaves
(F) whereby this instrument announces the third of the d-minor triad (and
later establishes the 3-bar phrase structure).  F was the only possible
timpani octave he could write for in his day due to limitations in range of
instruments of the day.  A more important driving factor may be the vocal
"friendliness" of the key of D for the human voice (but that's less
interesting to an instrumentalist like me!).
Wagner's Ring cycle begins in Eb and ends in Db.  Why?  Perhaps the Eb
prelude to Das Rheingold was driven by the friendliness of this key to the
horns, who establish the nature motif (based on the natural overtone
series).  The final Valhalla motif is inextricably linked to Db and here I
am stumped as to a possible reason - other than speculation that the use of
so many flats lends a darkness and richness to the brass by virtue of the
increased use of valve combinations necessitated by this key.
We do know that Wagner (like most, if not all composers) composed at the
keyboard.  What we should not forget is that orchestral works are generally
conceived orchestrally, and that non-pianistic considerations are likely to
be the driving force behind key selection for orchestral works.
Of course piano works (which have been the subject of most of the
discussion) are a whole different ballgame.  
Gary Evoniuk
Durham, NC