static Grob *accidentals (Grob *me);
static Slice head_positions_interval (Grob *me);
static Grob *first_head (Grob *me);
+ static Interval calc_main_heads_extent (Grob *me);
static Grob *get_rest (Grob *me);
static void set_stem (Grob *me, Grob *);
static void add_head (Grob *me, Grob *);