An orchestra of about 30 people are practicing on the stage of what appears to be an auditorium full of green chairs.
A rock band plays for a crowded bar.
An orchestra and a rock band are two distinct groups.  One is in an auditorium and the other is in a bar.
exists e1 x1 x2 x3.(n_stage(x3) & exists e2 p1 x4.(n_thing(x4) & on(e1,x3) & of(x3,x4) & Topic(e2,p1) & Actor(e2,x4) & v_appear(e2) & exists p2 s1 s2 x5 x6 x7.((x4 = x5) & of(s1,x7) & n_chair(x7) & a_green(s2) & Theme(s2,x7) & Theme(s1,x6) & a_full(s1) & (x5 = x6) & n_auditorium(x5))) & Actor(e1,x1) & v_practice(e1) & of(x1,x2) & n_people(x2) & n_date(x2) & a_date_day_30(x2) & a_date_day_30(x2) & r_about(x2) & n_orchestra(x1))
exists e1 s1 x1 x2 x3.(for(e1,x3) & n_bar(x3) & a_crowded(s1) & Theme(s1,x3) & Actor(e1,x1) & v_play(e1) & n_band(x1) & of(x1,x2) & n_rock(x2))