%% http://lsr.di.unimi.it/LSR/Item?u=1&id=900
%% <= http://lilypond.1069038.n5.nabble.com/Old-Bass-Clef-td28833.html
% add by P.P.Schneider on March 2014. Edited on June. 2017.

%% Path drawing:
my-clef =
#(ly:make-stencil
  `(path 0.001
     (moveto   -0.10  -0.35
      curveto  -0.10  -1.11   0.48  -1.80   1.25  -1.80
      curveto   1.75  -1.80   2.20  -1.60   2.50  -1.05
      curveto   2.55  -0.95   2.50  -0.90   2.43  -0.95
      curveto   2.20  -1.17   1.90  -1.48   1.45  -1.48
      curveto   0.70  -1.48   0.15  -0.85   0.15  -0.15
      curveto   0.15   0.45   0.62   0.83   1.05   0.83
      curveto   1.55   0.83   1.90   0.50   1.90   0.05
      curveto   1.90  -0.35   1.55  -0.71   1.20  -0.71
      curveto   0.80  -0.71   0.60  -0.40   0.63  -0.17
      curveto   0.75  -0.30   0.90  -0.31   1.00  -0.31
      curveto   1.20  -0.31   1.38  -0.10   1.38   0.15
      curveto   1.38   0.35   1.20   0.55   0.95   0.55
      curveto   0.60   0.52   0.39   0.25   0.39  -0.05
      curveto   0.39  -0.52   0.62  -0.89   1.20  -0.89
      curveto   1.65  -0.89   2.07  -0.50   2.07   0.10
      curveto   2.07   0.66   1.56   1.01   1.05   1.01
      curveto   0.28   1.01  -0.10   0.35  -0.10  -0.35
      moveto    2.42   0.20
      curveto   2.54   0.20   2.64   0.30   2.64   0.42
      curveto   2.64   0.54   2.54   0.64   2.42   0.64
      curveto   2.30   0.64   2.20   0.54   2.20   0.42
      curveto   2.20   0.30   2.30   0.20   2.42   0.20
      moveto    2.42  -0.20
      curveto   2.54  -0.20   2.64  -0.30   2.64  -0.42
      curveto   2.64  -0.54   2.54  -0.64   2.42  -0.64
      curveto   2.30  -0.64   2.20  -0.54   2.20  -0.42
      curveto   2.20  -0.30   2.30  -0.20   2.42  -0.20
      closepath)
     round round #t)
   (cons -0.1 2.65)
   (cons -1.3 1))

\layout {
  \context {
    \Score
    \override Clef.stencil = 
      #(lambda (grob) 
         (let* ((sz (ly:grob-property grob 'font-size 0)) 
                (mlt (magstep sz))
                (glyph (ly:grob-property grob 'glyph-name))) 
                 (cond
                  ((equal? glyph "clefs.F")  
                     (ly:stencil-scale my-clef (* 1 mlt) (* 1 mlt)))
                  ((equal? glyph "clefs.F_change")  
                    (ly:stencil-scale my-clef (* .8 mlt) (* .8 mlt)))
                  (else (ly:clef::print grob)))))
  }
}

%% Test:
#(set-global-staff-size 30)

\new GrandStaff <<
  \new Staff { 
    \clef G c'1 
    \clef F c 
    \clef G c' 
    <<
      a,
      \new CueVoice {
        %% Does not work:
        %\cueClef F
        \once\override Staff.Clef.font-size = #-4
        \clef F 
        f^"cue"
      }
    >>
  }
  \new Staff  {
    \clef F c1 
    \clef G c' 
    \clef "F^8" c' f
  }
>>