Re: enharmonic transposition of key signatures?

[Keith OHara]

Shevek <saul <at> saultobin.com> writes:

> I have a situation [with transposing instruments]
> and I would like to have the second key display as D flat, 
> rather than as C sharp. 

> \language "english"
> global = {\key c \major   s1*2   \key b \major   s1*2 }
 
In this situation (and also when transcribing music that omits the key
signature for brass instruments) the key signature is not really global.
I recommend that you include the key changes with the note entry,
especially if you are entering the notes with the instrument in mind.  

If you need to enter the notes in concert pitch (maybe using keyboard
entry) then it seems you need to change not only the key signature
but the played notes as well.  You can ask LilyPond to consider the 
instrument to be "Clarinet in A-sharp" while the music is in the key
of concert B major.

music = \relative c' { \transposition c'
  c4 d e f | g f e d | cs e fs gs | as2 b | }

\addQuote "m" << \music \global >>

{ s1*0 % work around bug with quote voices
  \transposition bf           % I am a B-flat Clarinet
  \quoteDuring #"m" s1*2
  \bar"||" \transposition as  % I am an A-sharp Clarinet
  \quoteDuring #"m" s1*2 }