Concert goers enjoy a show.
People are watching a rock band.
Just from enjoying a show doesn't mean theres a rock back they watch.
exists e1 x1 x2 x3.(Theme(e1,x3) & Actor(e1,x1) & v_enjoy(e1) & n_show(x3) & n_goer(x1) & (x1 = x2) & ne_nam_concert(x2))
exists e1 x1 x2 x3.(Theme(e1,x2) & Actor(e1,x1) & v_watch(e1) & n_band(x2) & of(x2,x3) & n_rock(x3) & n_people(x1))