|| (prop == ly_symbol2scm ("elements") && scm_is_pair (val))
|| (prop == ly_symbol2scm ("pitch-alist") && scm_is_pair (val)))
&& scm_is_false (scm_assq (prop, mutable_property_alist_)))
|| (prop == ly_symbol2scm ("elements") && scm_is_pair (val))
|| (prop == ly_symbol2scm ("pitch-alist") && scm_is_pair (val)))
&& scm_is_false (scm_assq (prop, mutable_property_alist_)))