How to typeset hymn-like vocal piece with piano intro and finale

[Steve Butner]

I am relatively new at LilyPond usage, though I've typeset about 5 pieces so
far.   Most have been piano music but a couple have been choral music.  I've
recently typeset a choral piece (hymn-like, two-staff layout) using the Hymn
setup snippet below (obtained from the LilyPond samples repository).

The Hymn setup template I started with looks like the code included below.  My
question is how I can modify it to put a short (about 4 measures) piano
introduction on it ... i.e. no lyrics in the intro portion.   Also, at the end,
I need to put out a 4-bar piano-only finale.

I have been able to get reasonably close to what I want by using _ in the lyrics
to skip over the initial intro but I'm wondering if there may be a better, more
correct (and direct) way to do what I need.   Any suggestions are greatly
appreciated.

\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"
        }