A man is playing an acoustic guitar.
A person is singing.
Not all man playing an acoustic guitar is singing.
exists e1 s1 x1 x2.(Theme(e1,x2) & Actor(e1,x1) & v_play(e1) & n_guitar(x2) & a_acoustic(s1) & Theme(s1,x2) & n_man(x1))
exists e1 x1.(Actor(e1,x1) & v_sing(e1) & n_person(x1))