Broken Crescendo Hairpin

In order to make parts of a crescendo hairpin invisible, the following method is used: A white rectangle is drawn on top of the respective part of the crescendo hairpin, making it invisible. The rectangle is defined as postscript code within a text markup.

The markup command with-dimensions tells LilyPond to consider only the bottom edge of the rectangle when spacing it against the hairpin. The property staff-padding prevents the rectangle from fitting between the hairpin and staff.

Make sure the hairpin is in a lower layer than the text markup to draw the rectangle over the hairpin.

\version "2.24.0"

\relative c' {
  <<
    {
      \dynamicUp
      r2 r16 c'8.\pp r4
    }
    \\
    {
      \override DynamicLineSpanner.layer = #0
      des,2\mf\< ~
      \override TextScript.layer = #2
      \once\override TextScript.staff-padding = #6
      \once\override TextScript.vertical-skylines = #'()
      des16_\markup \with-dimensions #'(2 . 7) #'(0 . 0)
                    \with-color #white
                    \filled-box #'(2 . 7) #'(0 . 2) #0
      r8. des4 ~ des16->\sff r8.
    }
  >>
}