Three people on stage singing and playing instruments.
 Three people giving a charitable concert.
Three people singing and playing instruments is a concert, but not necessarily a charitable concert.
exists x1 x2 x3 x4 x5.(a_topic(x1) & on(x1,x2) & n_instrument(x2) & of(x2,x5) & n_playing(x5) & of(x2,x4) & n_singing(x4) & of(x2,x3) & n_stage(x3) & n_people(x1) & card_eq_3(x1))
exists e1 s1 x1 x2 x3.(a_topic(x1) & Theme(e1,x3) & Actor(e1,x2) & v_give(e1) & n_concert(x3) & a_charitable(s1) & Theme(s1,x3) & (x1 = x2) & n_people(x1) & card_eq_3(x1))