View source for Adjusting slur positions vertically

Using <code>\override Slur.positions</code> it is possible to set the vertical position of the start and end points of a slur to absolute values (or rather, forcing LilyPond's slur algorithm to consider these values as desired). In many cases, this means a lot of trial and error until good values are found. You probably have tried the <code>\offset</code> command next just to find out that it doesn't work for slurs, emitting a warning instead.

The code in this snippet allows you to tweak the vertical start and end positions by specifying ''relative'' changes, similar to <code>\offset</code>.

Syntax: <code>\offsetPositions #'(<var>dy1</var> . <var>dy2</var>)</code>

<lilypond version="2.24">
offsetPositions =
#(define-music-function (offsets) (number-pair?)
  #{
     \once \override Slur.control-points =
       #(lambda (grob)
          (match-let ((((_ . y1) _ _ (_ . y2))
                       (ly:slur::calc-control-points grob))
                      ((off1 . off2) offsets))
            (set! (ly:grob-property grob 'positions)
                  (cons (+ y1 off1) (+ y2 off2)))
            (ly:slur::calc-control-points grob)))
  #})

\relative c'' {
  c4(^"default" c, d2)
  \offsetPositions #'(0 . 1)
  c'4(^"(0 . 1)" c, d2)
  \offsetPositions #'(0 . 2)
  c'4(^"(0 . 2)" c, d2)
  \bar "||"
  g4(^"default" a d'2)
  \offsetPositions #'(1 . 0)
  g,,4(^"(1 . 0)" a d'2)
  \offsetPositions #'(2 . 0)
  g,,4(^"(2 . 0)" a d'2)
}
</lilypond>

[[Category:Expressive marks]]
[[Category:Tweaks and overrides]]
[[Category:Scheme]]
[[Category:Included in the official documentation]]
[[Category:Snippet]]