String number extender lines
Make an extender line for string number indications, showing that a series of notes is supposed to be played all on the same string.
stringNumberSpanner = #(define-music-function (StringNumber) (string?) #{ \override TextSpanner.style = #'solid \override TextSpanner.font-size = #-5 \override TextSpanner.bound-details.left.stencil-align-dir-y = #CENTER \override TextSpanner.bound-details.left.text = \markup { \circle \number $StringNumber } #}) \relative c { \clef "treble_8" \stringNumberSpanner "5" \textSpannerDown a8\startTextSpan b c d e f\stopTextSpan \stringNumberSpanner "4" g\startTextSpan a bes4 a g2\stopTextSpan }