string to_type = ly_symbol2string (get_music ()->get_property ("change-to-type"));
string to_id = ly_scm2string (get_music ()->get_property ("change-to-id"));
string to_type = ly_symbol2string (get_music ()->get_property ("change-to-type"));
string to_id = ly_scm2string (get_music ()->get_property ("change-to-id"));