2.8 Inline Scheme code

TODO: after this section had been written, LilyPond has improved to the point that finding a simple example where one would have to revert to Scheme has become rather hard.

Until this section gets a rewrite, let’s pretend we don’t know.

The main disadvantage of \tweak is its syntactical inflexibility. For example, the following produces a syntax error (or rather, it did so at some point in the past).

F = \tweak font-size #-3 -\flageolet

\relative c'' {
  c4^\F c4_\F

Using Scheme, this problem can be avoided. The route to the result is given in Adding articulation to notes (example), especially how to use \displayMusic as a helping guide.

F = #(let ((m (make-music 'ArticulationEvent
                          'articulation-type "flageolet")))
       (set! (ly:music-property m 'tweaks)
             (acons 'font-size -3
                    (ly:music-property m 'tweaks)))

\relative c'' {
  c4^\F c4_\F

Here, the tweaks properties of the flageolet object m (created with make-music) are extracted with ly:music-property, a new key-value pair to change the font size is prepended to the property list with the acons Scheme function, and the result is finally written back with set!. The last element of the let block is the return value, m itself.

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LilyPond — Extending v2.18.2 (stable-branch).