Figured bass in parentheses

Put figured bass in parentheses with a Scheme function. See also Parenthesize a group of notes using a Scheme function.

\version "2.24"

startParenthesis =
  \once \override Parentheses.stencils =
    #(lambda (grob)
       (let ((par-list (parentheses-interface::calc-parenthesis-stencils grob)))
         (list (first par-list) point-stencil)))

endParenthesis =
  \once \override Parentheses.stencils =
    #(lambda (grob)
       (let ((par-list (parentheses-interface::calc-parenthesis-stencils grob)))
         (list point-stencil (second par-list))))

<<
  \time 12/8
  \new Staff { \clef "F" d4 8 4 8 8 8 4 8 }
  \new FiguredBass \figuremode {
    \parenthesize <6>4.
    \override Parentheses.font-size = #2
    \parenthesize <7 4>4
    \startParenthesis \parenthesize <6 4>8 <5 3> <4 2>
    \endParenthesis \parenthesize <3 1>4.
  }
>>