It has always been customary to spell the dim7 chord with as few
accidentals as possible, regardless. Its symmetrical nature makes it
irrational to spell it with double flats, not to mention triple flats. A
composer may well specify a double flat in a dim7 when in the process
of composition, but it usually gets changed, even in the notation,
before it sees print.
Sheet music chords are not there for analysis, and they are not there
to make statements about the tonality or mode, because these things are
irrelevant to quick recognition, which should be notation's *only*
concern. It is altogether rational to have a Dbb in the notation and a C
in a chord or vice versa, because *often* the vertical harmony and the
melodic structure do not have the same logic, and there is nothing
wrong with that. If it works, it works. Or not.
Suppose I write a tune that has an augmented 11th chord and the
aug 11 is the melody note. I didn't have the 5th anyway, and I find that
I have run out ot horns or fingers and get rid of the ninth. Do I have
to
go back and change all the sharps to flats because now I have a 7b5
chord?
If you are trying to specify chords and get a program to write parts
for you, quit it. Do something more worthwhile.
For analysis, you want the kind of academic chord notation that Piston
used. Why would anyone ever want to publish music that way unless
he/she were writing a textbook? Why should lilypond be expected to do
all the thinking for people who know enough to publish textbooks?
