%%LSR see https://lists.gnu.org/archive/html/lilypond-user-fr/2020-06/msg00119.html

%%%%%% 2.18 compatibility -- remove for 2.20 onwards %%%%%%

#(define-public (music-type-predicate types)
  "Returns a predicate function that can be used for checking
music to have one of the types listed in @var{types}."
  (if (cheap-list? types)
      (lambda (m)
        (any (lambda (t) (music-is-of-type? m t)) types))
      (lambda (m) (music-is-of-type? m types))))

#(define-public (get-tweakable-music mus)
  "When tweaking music, returns a list of music expressions where the
tweaks should be applied.  Relevant for music wrappers and event
chords."
  (cond ((music-is-of-type? mus 'music-wrapper-music)
         (get-tweakable-music (ly:music-property mus 'element)))
        ((music-is-of-type? mus 'event-chord)
         (filter (music-type-predicate 'rhythmic-event)
                 (ly:music-property mus 'elements)))
        (else (list mus))))

%%%%%%        End 2.18 compatibility definitions     %%%%%%

extend =
#(define-music-function (m) (ly:music?)
   (let* ((x-markup (markup #:normal-text #:fontsize 5 #:bold "×"))
          (x-fingering (make-music 'FingeringEvent 'text x-markup))
          (m-note (car (get-tweakable-music m)))
          (n (make-music 'NoteEvent
                         'duration (ly:music-property m-note 'duration)
                         'pitch (ly:music-property m-note 'pitch)
                         'articulations (list x-fingering)))
          (x-id (format #f "\"~a\"" (+ 100 (random 899)))))
     (or (eq? m m-note)
         (set! n (make-event-chord (list n))))
     #{
       \applyContext #(lambda (ctx)
                        (ly:context-set-property!
                         (ly:context-parent ctx) 'fingeringOrientations
                         (ly:context-property ctx 'fingeringOrientations)))
       \context Voice <<
         $m \new Voice = $x-id \scaleDurations 1/2 {
           \hideNotes \textLengthOn \omit Flag \omit Dots
           \applyContext #(lambda (ctx)
                            (ly:context-set-property!
                             ctx 'fingeringOrientations
                             (ly:context-property
                              (ly:context-parent ctx)
                              'fingeringOrientations)))
           s $n }
       >> #}))

{
  \clef bass
  \extend e'2-3 fis'-4
  \set fingeringOrientations = #'(down)
  \extend <e,-1> <fis,-2>
}