;; a callback for custom fret labels
-(define-public ((tab-note-head::print-custom-fret-label fret) grob)
+(define ((tab-note-head::print-custom-fret-label fret) grob)
(ly:grob-set-property! grob 'text fret)
(tab-note-head::print grob))
+(export tab-note-head::print-custom-fret-label)
(define-public (tab-note-head::print grob)
(define (is-harmonic? grob)