The brass section of an orchestra, mostly school-aged, performs a piece.
The whole orchestra is performing the current part of the score.
The brass section is not the whole orchestra.
exists e1 s1 x1 x2 x3 x4 x5.(n_section(x1) & of(x1,x2) & n_brass(x2) & Theme(e1,x5) & Actor(e1,x1) & v_perform(e1) & n_piece(x5) & r_mostly(s1) & Theme(s1,x4) & a_school-aged(s1) & (x1 = x4) & of(x1,x3) & n_orchestra(x3))
exists e1 s1 s2 x1 x2 x3.(n_score(x3) & n_part(x2) & a_current(s2) & Theme(s2,x2) & n_orchestra(x1) & a_whole(s1) & Theme(s1,x1) & Theme(e1,x2) & Actor(e1,x1) & v_perform(e1) & of(x2,x3))