Re: instrumentSwitch and addInstrumentDefinition use

[Keith OHara]

On Sun, 11 Jan 2015 12:36:43 -0800, Kieren MacMillan <address@hidden> wrote:

> > So LilyPond does not store a global key signature.
>
> No, but as you well know, many (most?) Lilypounders abstract the key signature 
> (etc.)
> into their own global [variable](s).

Right, but LilyPond doesn't know if that is the concert-pitch key (nor does she 
require all instruments to be playing in the same concert-pitch key).  I 
thought that would make automatic generation of key signature hard, but...
> > We could, I think, keep this organization, and write a
> > "\tranpositionUpdateKey bes"  that looks up the old key-signature and old
> > transposition on the Staff, figures the concert key, applies the new
> > transposition, figures the new key-signature for the new transposition
> > and sets that new key signature.
>
> Why can that not be rolled into an improved instrumentSwitch?

It could.  The old instrumentDefinition, however, had no advantage over just 
collecting the instrument-switch settings in a variable, and was harder to use.

> > I just write an explicit \key d\major at the instrument switch when needed
>
> This is one of the great banes of my current Lilypond existence — as a writer 
> of musical theatre and band/orchestral music, I need to change instruments and 
> keys all the time, very often in the middle of a section (w.r.t. key 
> signature). Trying to remember to explicitly add key signatures etc. — and tag 
> them as necessary — is quite frustrating, time-consuming, and error-prone.

I guess you enter the notes in concert pitch, then ?
Do you use the \quoteDuring mechanism (as below) or Jan-Peter's 
auto-transposing engraver to generate the engraved pitches for each instrument?


\version "2.19.15"
transpositionUpdateKey =
#(define-music-function (parser location new-transposition) (ly:pitch?)
   (_i "Set instrument transposition and, based on the previous
transposition and key, generate the key-change to keep the sounding key.")
   (define (generate-key-change c)
     (define (same-scale-step? a b) (= (car a) (car b)))
     (let* ((old-alt (delete-duplicates!
                        (append (ly:context-property c 'keyAlterations)
                                major)
                        same-scale-step?))
            (old-tonic (ly:context-property c 'tonic (ly:make-pitch 0 0 0)))
            (old-transp (ly:context-property c 'instrumentTransposition
                           (ly:make-pitch 0 0 0)))
            (delta (ly:pitch-diff old-transp new-transposition))
            (new-alt (ly:transpose-key-alist old-alt delta))
            (new-tonic (ly:pitch-transpose old-tonic delta))
            (sev (ly:make-stream-event `(key-change-event)
                    `((pitch-alist . ,new-alt)
                      (tonic . ,new-tonic)))))
     (ly:broadcast (ly:context-event-source c) sev)))
   #{
     \applyContext #generate-key-change
     \transposition $new-transposition
   #} )


prepClarinet = { \set Staff.shortInstrumentName="Clar"
                <>^\markup\italic\center-align "pick up clarinet" }
clarinet = { <>^\markup\bold"Clarinet"
             \once\set Staff.whichBar = "||"
             \transpositionUpdateKey bes }

concertBandEdition = {
  s1*3 \tag#'Sue \prepClarinet
  s1 \mark"All Reeds" \tag#'Sue \clarinet}

tune =  { \key c\major \repeat unfold 4 {c'4 e' g' b' R1} }
backup = { \key c\major \repeat unfold 8 {c'4 e' g' b' } }
\addQuote "tune" \tune

<< \new Staff \with { instrumentName="horn in F" }
   \keepWithTag#'Sue <<
      \concertBandEdition \transposition f
      \quoteDuring "tune" #(skip-of-length tune) >>
   \new Staff \with { instrumentName="alto clarinet" }
   \keepWithTag#'Joe <<
      \concertBandEdition \transposition es
      \transpose es c' \backup >>>>