question about lyrics changing via \set associatedVoice

[Steven Butner]

I'm trying to engrave a 4-part vocal piece that has a single line of 
lyrics that is associated with one of the voices at a time.  I've chosen 
to use the Hymn-snippet.ly (see attachment) as the base for this job 
though it had 4 stanzas so I did a bit of simple adaptation to make it 
more suited to my needs.

The problem I'm facing now is that the "melody" to which the single line 
of lyrics is associated begins in the alto voice and then later it moves 
into the tenor voice.   I've tried inserting the command   \set 
associatedVoice = #"three"  one syllable before the point where the 
voice association needs to change to tenor but what happens is simply 
that the lyrics stop happening altogether (at that point).   My thinking 
is that at the point in the lyrics block where the "\set 
associatedVoice" construct was used, the voice named "three" hasn't been 
seen yet ..... in other words an order-related problem.  Unfortunately, 
I don't have a good enough understanding of the scoping and ordering 
rules underlying Lilypond that I can find a solution.

Any help on this is greatly appreciated!    I've attached the \layout 
block that I'm using, hoping to clarify the setup in use.  Note that 
there is nothing fancy happening in the lyrics contained in the variable 
"verse".   The content of "verse" is something like

verse = \lyricmode { The words are here etc. etc.  \set associatedVoice 
= #"three" and then the words for the tenor continue here. }

Any guidance or suggestions  for fixing the setup so that the voice 
association can move between alto (set in the top staff) and tenor (set 
in the bottom staff) would be greatly appreciated.

    Thanks ...
    Steven Butner

\header {       

                title = "Hymn Template"
                subtitle = ""
                tagline = ""   
                poet = ""
                composer = ""   

                        
}

#(set-global-staff-size 20)     
\include "english.ly"



upperOne = 
        \relative a'{
        \time 4/4

        \voiceOne
        a4 b c d a b c d \break
                }
        

upperTwo =  
        \relative a'{

        \voiceTwo
        d,4 e f g d e f g
}


lowerOne =      
        \relative a {
        \time 4/4

        \voiceOne
        a4 b c d a b c d
        
} 

lowerTwo =   
        \relative c {

        \voiceTwo
        d4 e f g d e f g
}




firstverse = \lyricmode {
        La la la la la la la la
     }

secondverse = \lyricmode {
        Do do do do do do do do
        }

thirdverse = \lyricmode {
        Re re re re re re re re
        }

fourthverse = \lyricmode {

        }

refrain = \lyricmode { so so so so so
        
        }






\score{ 
        \context StaffGroup<<

                \context Staff = "upper" 
                        
                        <<
                        \clef treble
                        \context Voice = "one" \upperOne
                        \context Voice = "two" \upperTwo 
                        >>
                        
                \lyricsto "one" \new Lyrics {
                                        \set stanza = "1. "
                                        \firstverse 
                                        }

                \lyricsto "one" \new Lyrics {
                                        \set stanza = "2. "
                                        \secondverse 
                                        }

                 \lyricsto "one" \new Lyrics {
                                        \set stanza = "3. "
                                        \thirdverse 
                                        }
                        
                \context Staff = "lower" <<
                                        
                                        \clef bass
                                        \context Voice = "one" \lowerOne
                                        \context Voice = "two" \lowerTwo
                                        >>
                >>



\layout {


                \context{\Lyrics
                minimumVerticalExtent = #'(-0.5 . 3)

                }       
                        
                \context{\StaffGroup
                \remove "Span_bar_engraver"
                }

                \context{\Staff
                minimumVerticalExtent = #'(-3 . 3)
                autoBeaming = ##t
                \unset melismaBusyProperties 
                }
                
                \context{\Score
                barNumberVisibility = #all-invisible
                }
        }


\midi { }                       
}
\paper {

        linewidth = 6\in 
        indent = 0
        pagenumber = "no"
        }

\score{ 
        \context StaffGroup<<

                \context Staff = "upper" 
                        
                        <<
                        \clef treble
                        \context Voice = "one" \upperOne
                        \context Voice = "two" \upperTwo 
                        >>
                        
                \lyricsto "two" \new Lyrics {
                                        %% \set stanza = "1. "
                                        \verse 
                                        }

                \context Staff = "lower" <<
                                        
                                        \clef bass
                                        \context Voice = "one" \lowerOne
                                        \context Voice = "two" \lowerTwo
                                        >>
                >>