Tweaking in scheme

[Peter Gentry]

Tweaking in scheme

The heart of the scheme procedure  I'm trying is

#(define (instrumentrange music instrument ) 
   (  ly:music? string? ) 
; extract the various portions of the music object
(let ((es (ly:music-property music 'elements))      
           (e   (ly:music-property music 'element)) 
           (p   (ly:music-property music 'pitch)));rebuild the pitch and if a 
changed pitch add the color tweak
...
...

(if (ly:pitch? p)
          (let ((new-pitch (naturalize-instrument-range p instrument)))
          (ly:music-set-property! music 'pitch new-pitch)
          (if (and (not (equal? p new-pitch)) (color? my-color))
              (ly:music-set-property! music 'tweaks
              (acons
                'color my-color
               (ly:music-property music 'tweaks))))))

     music))

This works fine and I have used \displayMusic to show the music stream to 
investigate other possible properties that can be
specified in this way.

I would like to specify note head style but this does not seem to appear as a 
property that can be applied in the acons list.
In display music there is a complex list

(make-music
'ContextSpeccedMusic
'contextt-type
'Bottom
'element
(make-music
 'OverrideProperty
'pop-first
#t
'grob-property-path
(list (quote style))
'grob-value
'harmonic
'symbol
'NoteHead))

Can this in any way be implimented by  the 'tweaks method. 

regards
Peter Gentry