A stem-centered triangle notehead in LilyPond

How do we get a stem-centered triangle notehead in LilyPond?

Max implemented an answer last year reusing the triangle- or do-shaped notehead from the shape notes series. Here's the first example.



To me the example shows two different series of notes. The first four notes show a type of "inward-pointing" orientation while the last four notes show a type of "outward-pointing" orientation.

Later Max sent even more examples.



These are perfect. The outward-pointing triangles in measure two will handle both Sciarrino's lip- and tongue-pizzicati and also the "play the highest pitch, whatever that is" symbol in Penderecki. The inward-pointing triangles in measure three are amazingly odd and so visually distinct, at the same time. To what use will they go? Maybe ingressive air or some type of reversed bowing or playing. There's definitely something decidedly "reversed" about these shapes.

Suppressing LilyPond clashing NoteColumn warnings

Stacked LilyPond voices can produce clashing NoteColumn warnings.

   \new Staff <<
      \new Voice {
         \override Stem #'direction = #up
         c''4 c''4 c''4 c''4
      }
      \new Voice {
         \override Stem #'transparent = ##t
         \override Stem #'length = #0
         \override NoteHead #'duration-log = #1
         e'4 e'4 e'4 e'4
      }
      \new Voice {
         \override Stem #'direction = #down
         c'4 c'4 c'4 c'4
      }
   >>


   Preprocessing graphical objects...
   348.ly:6:27: warning: ignoring too many clashing note columns
           } { c''4 c''4 c''4
                              c''4 }
   348.ly:6:22: warning: ignoring too many clashing note columns
           } { c''4 c''4
                         c''4 c''4 }
   348.ly:6:17: warning: ignoring too many clashing note columns
           } { c''4
                    c''4 c''4 c''4 }
   348.ly:6:12: warning: ignoring too many clashing note columns
           } {
               c''4 c''4 c''4 c''4 }

What's going on here is that the middle note of each 'chord' sets Stem #'transparent = ##t which renders stems transparent but causes clashing note column warnings.

The solution is to set \override NoteColumn #'ignore-collision = ##t somewhere in the score.