A group of people holding music instruments.
A young boy is practicing on the piano.
A young boy is not a group of people.
exists e1 x1 x2 x3 x4 x5.(a_topic(x1) & of(x1,x2) & Theme(e1,x4) & Actor(e1,x3) & v_hold(e1) & n_instrument(x4) & of(x4,x5) & n_music(x5) & (x2 = x3) & n_people(x2) & n_group(x1))
exists e1 s1 x1 x2.(n_piano(x2) & on(e1,x2) & Actor(e1,x1) & v_practice(e1) & n_boy(x1) & a_young(s1) & Theme(s1,x1))