A man is playing an instrument.
A man playing a guitar.
A guitar is an instrument.
exists e1 x1 x2.(Theme(e1,x2) & Actor(e1,x1) & v_play(e1) & n_instrument(x2) & n_man(x1))
exists e1 x1 x2 x3.(a_topic(x1) & Theme(e1,x3) & Actor(e1,x2) & v_play(e1) & n_guitar(x3) & (x1 = x2) & n_man(x1))