A guitar player sings on a stage.
The person is performing music.
We know that the person is performing music because they are a guitar player.
exists x1 x2 x3 x4.(a_topic(x1) & on(x1,x4) & n_stage(x4) & n_sing(x1) & of(x1,x3) & n_player(x3) & of(x1,x2) & n_guitar(x2))
exists e1 x1 x2.(n_person(x1) & Theme(e1,x2) & Actor(e1,x1) & v_perform(e1) & n_music(x2))