Four people are playing drums.
The people are playing pianos.
One cannot be playing drums and playing playing pianos simultaneously.
exists e1 x1 x2.(Theme(e1,x2) & Actor(e1,x1) & v_play(e1) & n_drum(x2) & n_people(x1) & card_eq_4(x1))
exists e1 x1 x2.(n_people(x1) & Theme(e1,x2) & Actor(e1,x1) & v_play(e1) & n_piano(x2))