Man playing on the drums.
The man is playing a harp.
A harp is not the drums.
exists x1 x2 x3.(n_drum(x3) & a_topic(x1) & on(x1,x3) & n_playing(x1) & of(x1,x2) & n_man(x2))
exists e1 x1 x2.(n_man(x1) & Theme(e1,x2) & Actor(e1,x1) & v_play(e1) & n_harp(x2))