ADD_ACKNOWLEDGER (Script_engraver, rhythmic_head);
ADD_ACKNOWLEDGER (Script_engraver, stem);
ADD_ACKNOWLEDGER (Script_engraver, note_column);
ADD_ACKNOWLEDGER (Script_engraver, rhythmic_head);
ADD_ACKNOWLEDGER (Script_engraver, stem);
ADD_ACKNOWLEDGER (Script_engraver, note_column);