A group of people are at a rock concert.
A group of people are listening to music.
rock concert implies listening to music.
exists p1 x1 x2.(exists x3 x4.(at(x1,x3) & n_concert(x3) & of(x3,x4) & n_rock(x4)) & of(x1,x2) & n_people(x2) & n_group(x1))
exists e1 x1 x2 x3.(to(e1,x3) & n_music(x3) & Actor(e1,x1) & v_listen(e1) & of(x1,x2) & n_people(x2) & n_group(x1))