The band were playing in the stage.
The band did not play.
The band can't not play and play at the same time.
exists e1 x1 x2.(n_stage(x2) & n_band(x1) & in(e1,x2) & Actor(e1,x1) & v_play(e1))
exists x1.(n_band(x1) & -exists e1.(Actor(e1,x1) & v_play(e1)))