Align of Staff.instrumentName

[Till Rettig]

Hello,

I am trying to have an incipit as part of the instrument name for each 
staff.  The example explains how it should look.
This goes to far well if there are no lyrics, the systems get aligned. 
But if I add lyrics as in the example, there is obviously
added so much additional vertical space, that the new system gets too 
wide. It is vertically centered, and that way the
staff is too high. Is there a way to say that the instrumentName should 
be aligned at top?

Greetings
Till

\version "2.11.23"

global = {
  \set Score.skipBars = ##t
  \key g \major
  \time 4/4
  \skip 1*8 % the actual music

  % let finis bar go through all staves
  \override Staff.BarLine #'transparent = ##f

  % finis bar
  \bar "|."
}

  
discantusNotes = {
  \transpose c' c'' {
    \clef "treble"
    d'2. d'4 |
    b e' d'2 |
    c'4 e'4.( d'8 c' b |
    a4) b a2 |
    b4.( c'8 d'4) c'4 |
    \once \override NoteHead #'transparent = ##t c'1 |
    b\breve |
  }
}

discantusLyrics = \lyricmode {
  Ju -- bi -- |
  la -- te De -- |
  o, om --
  nis ter -- |
  ra, __ om- |
  "..." |
  -us. |
}


incipitDiscantus = \markup{
        \score{<<
                \new Voice = "incipita"
                {
        \set Staff.instrumentName="Discantus "
                \override NoteHead   #'style = #'neomensural
                \override Rest #'style = #'neomensural
                \override Staff.TimeSignature #'style = #'neomensural
                \cadenzaOn 
                \clef "neomensural-c1"
                \key f \major
                \time 2/2
                %uncomment next music line and comment the following line to see
                %that a plain markup doesn't interact with the spacing
                %c''1._"IV" c''2
                c''1. c''2 %two bars
                a'2 d''2 
                \skip 1*7 % seven bars
        }
        %uncomment next line to see correct spacing
                \new Lyrics \lyricsto "incipita" \lyricmode {  IV- } 
                >>
        \layout {
                \context {\Voice
                        \remove Ligature_bracket_engraver
                        \consists Mensural_ligature_engraver
                }
                line-width=4.5\cm 
        }
        }
}



\score {
  \new StaffGroup = choirStaff <<
    \new Voice =
      "discantusNotes" << \global 
      \set Staff.instrumentName=\incipitDiscantus   
      \discantusNotes >>
    \new Lyrics =
      "discantusLyrics" \lyricsto discantusNotes { \discantusLyrics }
    
  >>
  \layout {
        indent=5\cm
  }
}