This works out for a score that starts directly with multiple verses. If I start with a refrain, I still have the same problem:
\new StaffGroup {
<<
\new Staff {
\relative c' { c d e f g a b c }
}
\addlyrics{
a a a a
<<
{ b b b b }
\new Lyrics { c c c c }
>>
}
\new Staff {
\relative c' { c d e f g a b c }
}
>>
}
How do I position the lyrics line "c c c c" between the staves?