(to-relative-callback . ,ly:relative-octave-music::no-relative-callback)
(iterator-ctor . ,ly:music-wrapper-iterator::constructor)
(length-callback . ,ly:music-wrapper::length-callback)
(to-relative-callback . ,ly:relative-octave-music::no-relative-callback)
(iterator-ctor . ,ly:music-wrapper-iterator::constructor)
(length-callback . ,ly:music-wrapper::length-callback)