NoteEvent->grob ?

[Mark Polesky]

Given a NoteEvent expression, is there a way to access
the grob associated with it? I'm trying to access staff-
positions of notes within chords, and I want to do so
using music-map from within a music-function definition.
Maybe there's a better way, but this is the direction
I've taken so far.

(make-music
  'NoteEvent
  'duration
  (ly:make-duration 2 0 1 1)
  'pitch
  (ly:make-pitch 0 0 0))

I'm imagining something like this, but fill in the "..."

_______________________________


\version "2.13.1"

#(begin
(use-modules (ice-9 pretty-print))

(define (EventChord? music)
  (eq? (ly:music-property music 'name) 'EventChord))

(define (NoteEvent? music)
  (eq? (ly:music-property music 'name) 'NoteEvent))

(define (EventChord->NoteEvents EventChord)
  (filter NoteEvent?
          (ly:music-property EventChord 'elements)))

(define (NoteEvent->grob NoteEvent)
  ...)

(define (get-staff-position NoteEvent)
  (ly:grob-property (NoteEvent->grob NoteEvent)
                    'staff-position))

(define (get-staff-positions EventChord)
  (map get-staff-position
       (EventChord->NoteEvents EventChord)))

(define showPositions
  (define-music-function (parser location mus) (ly:music?)
    (music-map
     (lambda (x)
       (if (EventChord? x)
           (pretty-print (get-staff-positions x)))
       x)
     mus)))

) %end of (begin ...)

\relative { \showPositions { <c e g> <d f a> } }

%{
the desired output for this would be:
(-6 -4 -2)
(-5 -3 -1)
%}

_______________________________


Or is there a better access staff-positions for individual
notes in a chord? I know I can use an override like below,
but it's not the console display that I care about. I'd
like to be able to access staff-positions of each chord as
a list, or something like that, so I can use it, as I 
mentioned, with music-map within a music-function.

_______________________________

%% so, this doesn't really help me.
\relative {
  \override NoteHead #'stencil =
    #(lambda (grob)
      (pretty-print (ly:grob-staff-position grob))
      (ly:note-head::print grob))
      <c e g> <d f a>
}

Anyone?
Thanks.
- Mark