(reversed (reverse elements))
(element (ly:music-property music 'element))
(span-dir (ly:music-property music 'span-direction)))
(ly:music-set-property! music 'elements reversed)
(reversed (reverse elements))
(element (ly:music-property music 'element))
(span-dir (ly:music-property music 'span-direction)))
(ly:music-set-property! music 'elements reversed)