A woman is singing and playing guitar.
a man plays a tuba
It can either be a woman or a man. It can either be a guitar or a tuba.
exists e1 e2 x1 x2 x3 x4.(Theme(e2,x4) & Actor(e2,x3) & v_play(e2) & n_guitar(x4) & n_woman(x3) & Theme(e1,x2) & Actor(e1,x1) & v_sing(e1) & n_guitar(x2) & n_woman(x1))
exists e1 x1 x2.(Theme(e1,x2) & Actor(e1,x1) & v_play(e1) & n_tuba(x2) & n_man(x1))