\version "2.19.21"

%{
Allow editorial additions to underlay to be italic or [bracketed] (default).
Allow colouration in underlay, signifying reduced forces, to be
red or italic (default).

This only works with \lyricsto or \addlyrics due to the hardcoded duration.
Based on Simon Albrecht's code (see lilypond-user list 4 Dec 2015) 
with further help from David Kastrup and David Nalesnik.

Limitation: expect trouble if coloured and editorial lyrics overlap.
%}

%%% Coloured underlay %%%
coloured =
#(define-music-function (parser location syllable)(string?)
   #{
     \temporary \override LyricText.color = #red
     #(make-music
       'LyricEvent
       'text
       (format "~a" syllable)
       'duration
       (ly:make-duration 2))
   #})

endColour =
#(define-music-function (parser location syllable)(string?)
   #{
     #(make-music
       'LyricEvent
       'text
       (format "~a" syllable)
       'duration
       (ly:make-duration 2))
     \revert LyricText.color
   #})

wrapColour =
#(define-music-function (parser location syllable)(string?)
   #{
     \temporary \override LyricText.color = #red   
     #(make-music
       'LyricEvent
       'text
       (format "~a" syllable)
       'duration
       (ly:make-duration 2))
     \revert LyricText.color
   #})

%%% Italic underlay %%%
italic =
#(define-music-function (parser location syllable)(string?)
   #{
     \temporary \override LyricText.font-shape = #'italic
     #(make-music
       'LyricEvent
       'text
       (format "~a" syllable)
       'duration
       (ly:make-duration 2))
   #})

endItalic =
#(define-music-function (parser location syllable)(string?)
   #{
     #(make-music
       'LyricEvent
       'text
       (format "~a" syllable)
       'duration
       (ly:make-duration 2))
     \revert LyricText.font-shape
   #})

wrapItalic =
#(define-music-function (parser location syllable)(string?)
   #{
     \temporary \override LyricText.font-shape = #'italic
     #(make-music
       'LyricEvent
       'text
       (format "~a" syllable)
       'duration
       (ly:make-duration 2))
     \revert LyricText.font-shape
   #})
%}

%%% Bracketed underlay %%%
openBracket =
#(define-music-function (parser location syllable)(string?)
   (make-music
       'LyricEvent
       'text
       (format "[~a" syllable)
       'duration
       (ly:make-duration 2)))

closeBracket =
#(define-music-function (parser location syllable)(string?)
   (make-music
       'LyricEvent
       'text
       (format "~a]" syllable)
       'duration
       (ly:make-duration 2)))

wrapBrackets =
#(define-music-function (parser location syllable)(string?)
   (make-music
       'LyricEvent
       'text
       (format "[~a]" syllable)
       'duration
       (ly:make-duration 2)))

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%% Decide what we want:
#(define lyricColourationStyle
    (if (defined? 'lyricColourationStyle)
        lyricColourationStyle
        "italic"))

#(define lyricEditorialStyle
    (if (defined? 'lyricEditorialStyle)
        lyricEditorialStyle
        "bracketed"))

#(ly:message "lyricColourationStyle: ~a" lyricColourationStyle)
#(ly:message "lyricEditorialStyle: ~a" lyricEditorialStyle)

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
editorial = 
#(define-music-function (parser location syllable)(string?)
   (cond 
      ((string=? lyricEditorialStyle "italic")
        #{ \italic #syllable #})
      ((string=? lyricEditorialStyle "bracketed")
        #{ \openBracket #syllable #})
      (else (ly:message "invalid lyricEditorialStyle: ~a" lyricEditorialStyle)))
)
     
editorialEnding = 
#(define-music-function (parser location syllable)(string?)
   (cond 
      ((string=? lyricEditorialStyle "italic")
        #{ \endItalic #syllable #})
      ((string=? lyricEditorialStyle "bracketed")
        #{ \closeBracket #syllable #})
      (else (ly:message "invalid lyricEditorialStyle: ~a" lyricEditorialStyle)))
)

editorialWrap = 
#(define-music-function (parser location syllable)(string?)
   (cond 
      ((string=? lyricEditorialStyle "italic")
        #{ \wrapItalic #syllable #})
      ((string=? lyricEditorialStyle "bracketed")
        #{ \wrapBrackets #syllable #})
      (else (ly:message "invalid lyricEditorialStyle: ~a" lyricEditorialStyle)))
)

colour = 
#(define-music-function (parser location syllable)(string?)
   (cond 
      ((string=? lyricColourationStyle "italic")
        #{ \italic #syllable #})
      ((string=? lyricColourationStyle "red")
        #{ \coloured #syllable #})
      (else (ly:message "invalid lyricEditorialStyle: ~a" lyricEditorialStyle)))
)
     
colourEnding = 
#(define-music-function (parser location syllable)(string?)
   (cond 
      ((string=? lyricColourationStyle "italic")
        #{ \endItalic #syllable #})
      ((string=? lyricColourationStyle "red")
        #{ \endColour #syllable #})
      (else (ly:message "invalid lyricEditorialStyle: ~a" lyricEditorialStyle)))
)

colourWrap = 
#(define-music-function (parser location syllable)(string?)
   (cond 
      ((string=? lyricColourationStyle "italic")
        #{ \wrapItalic #syllable #})
      ((string=? lyricColourationStyle "red")
        #{ \wrapColour #syllable #})
      (else (ly:message "invalid lyricEditorialStyle: ~a" lyricEditorialStyle)))
)


%{ Test harness begins:
%#(define lyricColourationStyle "red")
%#(define lyricEditorialStyle "italic")

theNotes = {
  \relative { e''1 d c e d2 d c1 \break g' f e g f2 f e1 }
}

theWords = \lyricmode {
  Three \editorial blind \editorialEnding mice, see how \editorialWrap they run.
  Three \colour blind \colourEnding mice, see how \colourWrap they run.
}

\score
{
  \new StaffGroup
  <<
    \new Voice = "voice" \theNotes
    \new Lyrics \lyricsto "voice" \theWords
  >>
}
%%} %Test harness ends.