Quilismas in midi

I suspect that the answer to this will require me to rethink my approach, but I’m trying to figure out if a music function can alter the duration of the note which immediately precedes it.

The context: I’m typesetting chant using modern notation and have to deal with quilismas, those wiggly notes that you sometimes see.  Now, visually, I’ve accomplished this by defining the following function:

```
quilisma =
     \tweak NoteHead.stencil #ly:text-interface::print
     \tweak NoteHead.text \markup \musicglyph "scripts.prall"
     \tweak NoteHead.X-offset #0.8
     \etc
```

Which replaces the note head with a prall, the closest existing glyph I know of for this symbol.  It’s been good enough for me thus far, but now I’m trying to generate midi files out of the scores in order to practice and I’m running into problems.

Performance wise, a quilisma is interpreted as extending the note which precedes it (either dotting it or doubling it, depending on preference).  The note represented by the quilisma itself is of a normal duration.  Is there a way for the quilisma function to be modified to do this so that the midi comes out with the correct durations?

MWE

\version "2.26.0"
\language "english"

\layout {
    \context {
        \Score
        timing = ##f
    }
    \context {
        \Staff
        \remove "Time_signature_engraver"
    }
    \context {
        \Voice
        \omit Stem
        \override NoteHead.stem-attachment = #'(0 . 0)
        \slurUp
    }
}

quilisma =
     \tweak NoteHead.stencil #ly:text-interface::print
     \tweak NoteHead.text \markup \musicglyph "scripts.prall"
     \tweak NoteHead.X-offset #0.8
     \etc

\score {
    {
        e' \quilisma f' g'
    }
    \layout {}
    \midi {}
}

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Fr. Samuel, OSB
(R. Padraic Springuel)
St. Anselm’s Abbey
4501 South Dakota Ave, NE
Washington, DC, 20017
202-269-2300
(c) 202-853-7036

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