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2.3.4 Intermediate substitution functions

Intermediate substitution functions involve a mix of Scheme code and LilyPond code in the music expression to be returned.

Some \override commands require an argument consisting of a pair of numbers (called a cons cell in Scheme).

The pair can be directly passed into the music function, using a pair? variable:

manualBeam =
#(define-music-function
     (parser location beg-end)
     (pair?)
   #{
     \once \override Beam #'positions = #beg-end
   #})

\relative c' {
  \manualBeam #'(3 . 6) c8 d e f
}

Alternatively, the numbers making up the pair can be passed as separate arguments, and the Scheme code used to create the pair can be included in the music expression:

manualBeam =
#(define-music-function
     (parser location beg end)
     (number? number?)
   #{
     \once \override Beam #'positions = #(cons beg end)
   #})

\relative c' {
  \manualBeam #3 #6 c8 d e f
}

---

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