LilyPond: passing music symbols as arguments to a function / markup-command

Question

I am preparing in LilyPond a music book divided into many sections, each having a title. I want to keep the formatting of all titles in a single place, to make future format changes easier, and know two methods to do so: using \define-scheme-function, and using \define-markup-command -

#(define-markup-command (section_title_MC layout props text) (markup?)
  (interpret-markup layout props
   #{ 
     \markup \bold \fontsize #3 { #text } 
   #}))

section_title_SF = #(define-scheme-function
     (parser location text)(markup?)
   #{
      \markup \column {
      \bold \fontsize #3 { #text }
      }
   #})

\markup \section_title_MC "Etudes in C Major"

{
  \key c \major
  c'1
}
  

\section_title_SF "Etudes in G Major"

{
  \key g \major
  g'1
}

My problem is that neither method seem to respect music symbols, such as \flat and \sharp:

\markup \section_title_MC "Etudes in B \flat Major"

{
  \key bes \major
  bes'1
}

\section_title_SF "Etudes in E \flat Major"

{
  \key ees \major
  ees'1
}

Compare this with “direct” markup:

\markup {\bold \fontsize #3 { Etudes in B \flat Major }}

{
  \key bes \major
  bes'1
}

Will appreciate any help.

Answer 1

A string is a string.

#(define-markup-command (section_title_MC layout props text) (markup?)
  (interpret-markup layout props
   #{ 
     \markup \bold \fontsize #3 { #text } 
   #}))

section_title_SF = #(define-scheme-function
     (parser location text)(markup?)
   #{
      \markup \column {
      \bold \fontsize #3 { #text }
      }
   #})

\markup \section_title_MC \line { Etudes in \concat { B \raise #1 \flat } Major }

{
  \key bes \major
  bes'1
}


\section_title_SF \markup { Etudes in \concat { E \raise #1 \flat } Major }

{
  \key ees \major
  ees'1
}