\version "2.25.20"
%% SNIPPET %%
%%Adding indicators to staves which get split after a break
%%This snippet defines the:
%\splitStaffBarLine, convUpStaffBarLine and convDownStaffBarLine commands.
%These add arrows at a bar line, to denote that several voices sharing a staff will each continue on a staff of their own in the next system, or that voices split in this way recombine. 
#(define-markup-command (arrow-at-angle layout props angle-deg length fill)
   (number? number? boolean?)
   (let* (
           (PI-OVER-180 (/ (atan 1 1) 34))
           (degrees->radians (lambda (degrees) (* degrees PI-OVER-180)))
           (angle-rad (degrees->radians angle-deg))
           (target-x (* length (cos angle-rad)))
           (target-y (* length (sin angle-rad))))
     (interpret-markup layout props
       (markup
        #:translate (cons (/ target-x 2) (/ target-y 2))
        #:rotate angle-deg
        #:translate (cons (/ length -2) 0)
        #:concat (#:draw-line (cons length 0)
                   #:arrow-head X RIGHT fill)))))
splitStaffBarLineMarkup = \markup \with-dimensions #'(0 . 0) #'(0 . 0) {
  \combine
  \arrow-at-angle #45 #(sqrt 8) ##t
  \arrow-at-angle #-45 #(sqrt 8) ##t
}
splitStaffBarLine = {
  \once \override Staff.BarLine.stencil =
  #(lambda (grob)
     (ly:stencil-combine-at-edge
      (ly:bar-line::print grob)
      X RIGHT
      (grob-interpret-markup grob splitStaffBarLineMarkup)
      0))
  %\break
}
convDownStaffBarLine = {
  \once \override Staff.BarLine.stencil =
  #(lambda (grob)
     (ly:stencil-combine-at-edge
      (ly:bar-line::print grob)
      X RIGHT
      (grob-interpret-markup grob #{
        \markup\with-dimensions #'(0 . 0) #'(0 . 0) {
          \translate #'(0 . -.13)\arrow-at-angle #-30 #(sqrt 30) ##t
        }#})
      0))
  %\break
}
convUpStaffBarLine = {
  \once \override Staff.BarLine.stencil =
  #(lambda (grob)
     (ly:stencil-combine-at-edge
      (ly:bar-line::print grob)
      X RIGHT
      (grob-interpret-markup grob #{
        \markup\with-dimensions #'(0 . 0) #'(0 . 0) {
          \translate #'(0 . -3.70)\arrow-at-angle #30 #(sqrt 30) ##t
        }#})
      0))
  %\break
}
%%
switch = { \new Staff = "switch" 
 \with { \RemoveAllEmptyStaves } 
 { % switch staff code
 c''1 d'' e'' f''
 \stopStaff
 \splitStaffBarLine  s1
 \override Staff.StaffSymbol.line-positions = #'(-11 -9 -7 -5 -3)
 \set Staff.clefPosition = -9
 \set Staff.middleCPosition = -13
 \startStaff
 <<
   %% First let's create the lower staff (bass clef).
   \override Score.BreakAlignment.break-align-orders =
  #(make-vector 3 '(
                    staff-bar
                    clef
                   ))
  \clef bass
  \set Staff.clefPosition = -5
  \set Staff.middleCPosition = -1
  \set Staff.middleCClefPosition = -1
   { \repeat unfold 2 {c1 d e f} 
     \break % breaking the line just to test the converging together.
   \once \override Staff.Clef.X-extent = #'(-1 . 0)
   %{ Had to use this Clef.-X because the clef was going inside
   the initial left wall of the bar.%}
   c1 d e f
   \stopStaff \convUpStaffBarLine s1}
  %% Now to create the second staff (in this case, upper staff).
   {\new Staff 
   \with {
   \remove Time_signature_engraver
     alignAboveContext = "switch"
     \magnifyStaff #1
     \override VerticalAxisGroup.default-staff-staff-spacing =
     #'((basic-distance . 3)
        (minimum-distance . 4)
        (padding . 0)
        (stretchability . 10))
     %{firstClef = ##f%} }
   { % higher staff code
   \override Score.BreakAlignment.break-align-orders =
  #(make-vector 3 '(
                    staff-bar
                    clef
                   ))
  \clef treble
  \set Staff.clefPosition = -1
  \set Staff.middleCPosition = 1
  \set Staff.middleCClefPosition = 1
   { \repeat unfold 3 {c1 d e f} 
     \stopStaff \convDownStaffBarLine 
     s1}
   }} % end higher staff code & variable
>>
\revert Score.BreakAlignment.break-align-orders
\revert Staff.StaffSymbol.line-positions
\startStaff
\clef treble
\relative c'' {\time 5/8 {\repeat unfold 4 {c8 b a g a}}}
\once \override Score.TimeSignature.break-visibility = #'#(#f #t #t)
} % end Switch Staff
} % end Switch variable

MelodyInUnison = { \new Staff \with { \RemoveAllEmptyStaves }
{ % MelodyInUnison staff code
\relative c'' {{\repeat unfold 2 {c1 d e f}}}
} % end of MelodyInUnison Staff
} % end of MelodyInUnison variable

music = {
\MelodyInUnison
\break
\switch
\revert Score.BreakAlignment.break-align-orders
\revert Staff.StaffSymbol.line-positions
\break
\time 4/4
\MelodyInUnison
} % end music variable

\score { \music }