Lilypond glissando across piano staves

Question

I'm trying to typeset the glissando shown below using Lilypond:

There are examples in the docs but they weren't helpful.

My code:

\version "2.24.0"

upper = \relative{
\clef treble
\key c \major
\time 5/4
\override VoiceFollower.style = #'zigzag 
<c'' e fis a>2.\glissando
\change Staff = "lower"
<a,,, a'>4
\change Staff = "upper"
}

lower = \relative{
\clef bass
\key c \major
\time 5/4
<a c e>2. \skip 4 r4
}

\score {\new PianoStaff <<
  \new Staff = "upper" \upper
  \new Staff = "lower" \lower
  >>
\layout {}
\midi { }
}

gives me:

How do I fix this?

Answer 1

To accomplish this, set the \glissandoMap, which tells LilyPond which note within each chord to connect via the glissando line.

From the LilyPond documentation (link below):

A glissando can connect notes in chords. If anything other than a direct one-to-one pairing of the notes in the two chords is required the connections between the notes are defined by setting \glissandoMap, where the notes of a chord are assumed to be numbered from zero in the order in which they appear in the input ‘.ly’ file.

In the specific case here, add
\set glissandoMap = #'((3 . 1))
after the VoiceFollower setting.

For more on \glissandoMap see 1.3.3 Expressive marks as lines: Glissando in the LilyPond documentation.