How to pass `ly:music` to a `markup-command`

Question

I am attempting to create a lilypond markup command which will display a guitar chord fingering above the chord on a stave. The code I have so far follows:

#(define-markup-command (chord_and_fingering layout props
  chord fingering) (ly:music? string?)
  "…documentation…"
  (interpret-markup layout props
    #{ \markup { \center-column {
      \fret-diagram #(string-append "f:1;h:13;" fingering)
      \score {
        \new Staff {
          \clef "treble_8"
          \set fingeringOrientations = #'(left)
          #chord \bar "|."
        }
        \layout {
          \override Staff.TimeSignature #'stencil = ##f
          \override Staff.Clef #'transparent = ##t
        }
      }
    }}#}
))

It works okay, but I cannot figure out how to pass a music expression directly to it. That is, I can use it like this with a temporary variable:

a_C_major_chord = {
  <c-3 e-2 g-0 c'-1 e'-0>1
}

a_C_major = \markup {
  \chord_and_fingering
    #a_C_major_chord 
    #"6-x;5-3;4-2;3-o;2-1;1-o;"
}

But would like to use it like this, without:

a_C_major = \markup {
  \chord_and_fingering
    #{<c-3 e-2 g-0 c'-1 e'-0>1}
    #"6-x;5-3;4-2;3-o;2-1;1-o;"
}

This however doesn't work. Could someone tell me where I am going wrong and what is the correct syntax for this?

Thank-you for your time and help.

Answer 1

Well, you can use either

\notemode {<c-3 e-2 g-0 c'-1 e'-0>1}

or (you were almost there)

##{<c-3 e-2 g-0 c'-1 e'-0>1#}

Remember: # throws you from LilyPond input modes into Scheme and #{ introduces stuff in LilyPond syntax into Scheme. Here you are combining both and so need ##{ at the start.