A guitarist on stage playing and singing with his keyboardist in the background.
a guitarist is playing
we have the rephrasing of words  a guitarist playing
exists e1 x1 x2 x3 x4 x5 x6 x7.(n_background(x7) & a_topic(x1) & on(x1,x2) & subset_of(e1,x2) & with(e1,x6) & in(x6,x7) & n_keyboardist(x6) & of(x6,x1) & n_male(x1) & Actor(e1,x5) & v_sing(e1) & n_thing(x5) & subset_of(x3,x2) & n_playing(x3) & of(x3,x4) & n_stage(x4) & n_guitarist(x1))
exists e1 x1.(Actor(e1,x1) & v_play(e1) & n_guitarist(x1))