A singer of a band on stage.
The singer is singing the national anthem.
Singer on a stage does not have to be singing.  Other songs can be sung other than the national anthem.
exists x1 x2 x3.(a_topic(x1) & of(x1,x2) & on(x2,x3) & n_stage(x3) & n_band(x2) & n_singer(x1))
exists e1 s1 x1 x2.(n_anthem(x2) & a_national(s1) & Theme(s1,x2) & n_singer(x1) & Theme(e1,x2) & Actor(e1,x1) & v_sing(e1))