Re: Gis major key signature; Lily's key signature algorithm

[Torsten Hämmerle]

Hi Richard,

That's an interesting question, indeed...



Richard M wrote
> Why does LilyPond notate it one way, [...]

LilyPond uses a list keyAlterationOrder containing the order of alterations
printed.

It is defined as follows in engraver-init.ly:

  keyAlterationOrder = #`(
    (6 . ,FLAT) (2  . ,FLAT) (5 . ,FLAT ) (1  . ,FLAT) (4  . ,FLAT) (0  .
,FLAT) (3  . ,FLAT)
    (3 . ,SHARP) (0 . ,SHARP) (4 . ,SHARP) (1 . ,SHARP) (5 . ,SHARP) (2 .
,SHARP) (6 . ,SHARP)
    (6 . ,DOUBLE-FLAT) (2 . ,DOUBLE-FLAT) (5 . ,DOUBLE-FLAT ) (1 .
,DOUBLE-FLAT) (4 . ,DOUBLE-FLAT) (0 . ,DOUBLE-FLAT) (3 . ,DOUBLE-FLAT)
    (3  . ,DOUBLE-SHARP) (0 . ,DOUBLE-SHARP) (4 . ,DOUBLE-SHARP) (1 .
,DOUBLE-SHARP) (5 . ,DOUBLE-SHARP) (2 . ,DOUBLE-SHARP) (6 . ,DOUBLE-SHARP)
  )

(sorry for the bad formatting).

the numbers range from 0 to 6 with 0 = C ... 6 = B

translated into pitches, that will be
   Bb Eb Ab Db Gb Cb Fb
   F# C# G# D# A# E# B#
   Bbb Ebb Abb Dbb Gbb Cbb Fbb
   F## C## G## D## A## E## B##


That's why F## will be printed last.



Richard M wrote
> [...] and I'm wondering if there's an official source that determines how
> they are to be notated.

As to the "official" order of accidentals, Elaine Gould writes: "The order
of accidentals follows the 'cycle of fifths'."

This, unfortunately, is not very clear for the "theoretical keys" containing
double flats or double sharps.

*1st interpretation* (LilyPond's behaviour)
As the F## in G# major is the last accidental in the circle of fifths, so
it's printed last.

*2nd interpretation*
While the F## may be the last accidental, it's nevertheless replacing the F#
(the first sharp) and therefore should be printed first.

By the way, switching languages in Wikipedia, simple English or Polish will
show LilyPond's order. ;)

All the best,
Torsten




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