how to detect position of note on stave?

[Graham King]

I'm trying to replace a note with one of two special glyphs, depending
on the note's position on the stave:  if on the third line or above,
stem down, otherwise stem up.  Is it possible to extend the following
code to detect automatically (and independently of clef or
transposition) which glyph should be chosen?

\version "2.19.5"

#(define ((note-head-musicglyph name) grob)
(grob-interpret-markup grob (make-musicglyph-markup name)))
 
\score {
    \shiftDurations #-1 #0 {
        \relative c' {
            \time 4/2 
            c c c c
            \once \override NoteHead #'stencil = 
                #(note-head-musicglyph "noteheads.uM2mensural")
                % #(note-head-musicglyph "noteheads.dM2mensural")
            c1
        }}}

Thanks, in anticipation!

-- Graham King

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