An orchestra practicing their composition.
The orchestra is practicing a very difficult composition.
Not all compositions are difficult.
exists e1 x1 x2 x3.(a_topic(x1) & Theme(e1,x3) & Actor(e1,x2) & v_practice(e1) & n_composition(x3) & of(x3,x1) & n_thing(x1) & (x1 = x2) & n_orchestra(x1))
exists e1 s1 x1 x2.(n_orchestra(x1) & Theme(e1,x2) & Actor(e1,x1) & v_practice(e1) & n_composition(x2) & a_difficult(s1) & Theme(s1,x2) & r_very(x2))