the two boys playing guitar
Two boys are playing a concert in a nightclub.
The two boys could be playing guitar anywhere and for any reason.  Just because they are playing guitar does not mean they are playing a concert in a nightclub.
exists e1 x1 x2 x3.(n_boy(x1) & card_eq_2(x1) & a_topic(x1) & Theme(e1,x3) & Actor(e1,x2) & v_play(e1) & n_guitar(x3) & (x1 = x2))
exists e1 x1 x2 x3.(in(e1,x3) & n_nightclub(x3) & Theme(e1,x2) & Actor(e1,x1) & v_play(e1) & n_concert(x2) & n_boy(x1) & card_eq_2(x1))