\version "2.18.0"
myFunction =
#(lambda (grob)
(let* ((notehead-stl (ly:grob-property grob 'stencil))
;; for scaling your stencil according to font size
(fsz (ly:grob-property grob 'font-size 0.0))
(mult (magstep fsz)))
(set! (ly:grob-property grob 'stencil)
(ly:stencil-add
notehead-stl
(ly:stencil-scale
(make-connected-path-stencil
'((-1 0.5) ;; path coordinates
(-1 0)
(-0.5 0.2))
0.1 ;; line thickness
1 ;; X-axis scaling factor
1 ;; Y-axis scaling factor
#f ;; auto-connect path to origin point? (0 0)
#f) ;; filled path?
mult mult)))))
{
\override NoteHead.after-line-breaking = \myFunction
c'4 d' e' f'
}