ADD_ACKNOWLEDGER (Part_combine_engraver, note_head);
ADD_ACKNOWLEDGER (Part_combine_engraver, stem);
ADD_TRANSLATOR (Part_combine_engraver,
ADD_ACKNOWLEDGER (Part_combine_engraver, note_head);
ADD_ACKNOWLEDGER (Part_combine_engraver, stem);
ADD_TRANSLATOR (Part_combine_engraver,