1\version "2.21.6"
2
3\header {
4  texidoc = "Score level Vertical_align_engraver ignore axis
5  groups that are not spanners.  In this case, the @code{Devnull}
6  context has no Axis_group_engraver, so the NoteColumn appears like a
7  parent-less axis group; even so, the Score level alignment ignores
8  it."
9}
10
11<<
12  \new Devnull = "a" { s }
13  \new Staff { c' \change Staff = "a" c' }
14>>
15