+ fret-number string-number (length labels))
+ ".")))
+ (add-bass-string-nr ;; starting at zero
+ (- string-number string-count 1)))
+ (make-translate-scaled-markup '(0 . -0.5)
+ ;; For additional bass strings, we add zero up to three "/"-signs before
+ ;; the letter, even more bass strings will get numbers, starting with "4".
+ ;; In the rare case such a string isn't played open, we put out, eg."4b"
+ (make-concat-markup
+ (if (> string-number (+ string-count 4))
+ (list (number->string add-bass-string-nr)
+ (if (zero? fret-number) "" letter))
+ (list (make-string (max 0 add-bass-string-nr) #\/)
+ letter))))))