A band plays at a concert, while a crowd of people look on.
A marching band practicing in a gym.
A concert is the performance, not the practice.
exists e1 p1 x1 x2.(exists e2 p2 x3 x4.(exists s1.(Theme(s1,x3) & a_on(s1)) & Topic(e2,p2) & Actor(e2,x3) & v_look(e2) & of(x3,x4) & n_people(x4) & n_crowd(x3)) & while(e1,p1) & at(e1,x2) & n_concert(x2) & Actor(e1,x1) & v_play(e1) & n_band(x1))
exists e1 x1 x2 x3.(a_topic(x1) & in(x1,x3) & n_gym(x3) & n_practicing(x1) & of(x1,x2) & n_band(x2) & Actor(e1,x1) & v_march(e1))