glissando or something similar in drummmode

[Mason Hock]

I'm working on a percussion piece in which the performers play, in addition to 
unpitched percussion instruments, roto toms, which they occasionally play with 
one hand while adjusting the pitch of the other in order to achieve a glissando 
effect. Only the direction, maxima, and minima of the glissando is important, 
not the specific pitch at a given moment, so when this effect is used the 
performers would prefer to switch from a 5-line percussion staff to a 1-line 
staff indicating the rhythm and drawing the glissando direction.

Below is what I have so far. I'm happy with the transition to a 1-line staff 
and the notation of rhythm with headless stems, but the gliss line does not 
render. It makes sense that the gliss line would not render; since this is a 
DrumStaff the notes do not represent pitches, making a glissando meaningless. 
However, I do want to use a DrumStaff for the upitched passages, and I'm not 
sure how to turn DrumStaff into a Staff in the middle of the music.

Can anyone suggest (a) a better approach than what I'm trying or (b) a hack to 
make the glissando engraver draw glissandi between noteheads that Lilypond does 
not think represent pitches?

Thanks,

Mason 

--------------------------------------------------------------------
\version "2.19.82"

drumPitchNames.cy = #'cymbal
drumPitchNames.br = #'brakedrum
drumPitchNames.to = #'tom
drumPitchNames.ro = #'rototom
drumPitchNames.rt = #'rototomtop
drumPitchNames.ba = #'bassdrum
drumPitchNames.ta = #'tamtam

#(define drumstaff
  '((cymbal             xcircle         #f   3)
    (brakedrum          cross           #f   1)
    (tom                        default         #f  -1)
    (rototom            default         #f   0)
    (rototomtop         default         #f   4)
    (timpani            default         #f  -4)
    (bassdrum           default         #f  -3)
    (tamtam             harmonic-mixed  #f  -3)))

rotogliss = {
  \stopStaff
  \override Staff.StaffSymbol.line-positions = #'(0)
  \startStaff
}

normalstaff = {
  \stopStaff
  \revert Staff.StaffSymbol.line-positions
  \startStaff
}

glon = {
  \override NoteColumn.glissando-skip = ##t
  \hide NoteHead
}

gloff = {
  \revert NoteColumn.glissando-skip
  \undo \hide NoteHead
}

notes = \drummode {
  ba4 r <ro cy> <ro cy> |
  to16 to to to <to ro>8 <to ro> ro ro ro ro |
  \rotogliss
  ro \glissando \glon ro ro ro ro ro ro ro |
  \gloff rt16 rt rt rt rt8 \glissando \glon ro ro ro ro ro |
  ro ro ro ro \gloff \normalstaff ro ro ro ro |

}

\score {
   \new DrumStaff
    \with {
      drumStyleTable = #(alist->hash-table drumstaff)
    }
    \notes
  \layout {}
}
--------------------------------------------------------------------

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