#(define KEY-POS-LIST '(       
   (c    .    1) (cis  .  1.5) (des . 1.5) (d    .    2) (dis  .  2.5) (ees  .  2.5) (e   .  3) 
   (f    .    4) (fis  .  4.5) (ges . 4.5) (g    .    5) (gis  .  5.5) (aes  .  5.5) (a   .  6) 
   (ais  .  6.5) (bes  .  6.5) (b   .   7)))

#(define (black-key? num )
   (member num '(cis  des  dis  ees  fis  ges  gis  aes  ais  bes)) )

#(define (key-to-pos key ypos scale)
  (let ((keypos (assq key KEY-POS-LIST)))
   (if (not keypos)
    (ly:error (_ "keyboard diagram error - unknown note '~a'") key)
    (cons (* (- (cdr (assq key KEY-POS-LIST)) 0.5) scale) (+ (* (- scale 1) 0.32) ypos)))))

#(define (make-keys l1 width off height scale)
   (if (null? l1) 
       empty-stencil
       (ly:stencil-add 
          (ly:stencil-translate
            (make-line-stencil 0.1 0 0 0 height) 
               (cons (* (- (car l1) 1) scale) off ))
          (make-keys (cdr l1) width off height scale))))

#(define (make-keys-black l1 width off height scale)
   (if (null? l1) 
       empty-stencil
       (ly:stencil-add 
          (ly:stencil-translate
            (ly:round-filled-box `(0 . ,(* width scale)) `(0 . ,height) 0) 
               (cons (* (- (car l1) (/ width 2)) scale )  off))
          (make-keys-black (cdr l1) width off height scale))))

#(define (make-dot key scale)
  (if (black-key? key)
    (ly:stencil-in-color 
      (ly:stencil-translate (make-circle-stencil  (* 0.27 scale) 0 #t) (key-to-pos key 2.5 scale)) 1 1 1)
    (ly:stencil-translate (make-circle-stencil  (* 0.32 scale) 0 #t) (key-to-pos key 0.5 scale)) ))

#(define (make-dot-list l1 scale)
   (if (null? l1) 
       empty-stencil
       (ly:stencil-add 
          (make-dot (car l1) scale)
          (make-dot-list (cdr l1) scale ))))

#(define-markup-command (keys layout props arg1 arg2) (list? number?) 
    (ly:stencil-add
      (make-line-stencil 0.1 0 0 (* 7 arg2) 0)
      (make-line-stencil 0.1 0 6 (* 7 arg2)  6)
      (make-keys       '(1 2 3 4 5 6 7 8) 1    0 6 arg2)
      (make-keys-black '(1 2   4 5 6    ) 0.65 2 4 arg2)
      (make-dot-list arg1 arg2)))

key_scale=2.0

\relative c'' {
  \textLengthOn
  b4^\markup\keys #'(b) #1 r r2 r1
  b4^\markup\keys #'(b) #1.5 r r2 r1
  b4^\markup\keys #'(b) #key_scale r r2 r1
  a4^\markup\keys #'(a) #2.5 r r2 r1
  bes4^\markup\keys #'(bes) #3 r r2
}