On Fri, 2008-11-07 at 10:37 -0600, Jeremiah Benham wrote:
I began writing a real transposition script
(define chromatic_notes '(
("a" 0)
("b" 1)
("c" 2)
("d" 3)
("e" 4)
("f" 5)
("g" 6)))
(define sharp_list (list "a" "ais" "b" "c" "cis" "d" "dis" "e" "f"
"fis"
"g" "gis"))
(define transpose
(lambda (note modulate)
(list-ref sharp_list (+ modulate (car (cdr (assoc note
chromatic_notes)))))))
Am I on the right path with this.
I am not so sure that this is a good way to go. A transposition is not
defined by a single integer.
You need two, one would be the number of diatonic steps, the other
something to encode the number of additional sharps/flats.
So c->cis would be (0, 7)
an augmented unison (that is going for example from C-major to C#-
major)
c->cis'' would be (16, 7)
same plus two octaves
while
c->des would be (1, -5)
a minor second (going for example from C-major to Db-major)
my guess is that someone will have sorted out a neat way of
calculating
the amount to add/subtract to the enharmonic_shift for a given
transposition - a good place to look might be the LilyPond source
tarball.