People playing instruments on stage in front of blue banners.
A band is performing at a party.
Just because people play instruments in front of banners does not mean they're a band at a party.
exists e1 s1 x1 x2 x3 x4 x5 x6.(a_topic(x1) & in(e1,x5) & of(x5,x6) & n_banner(x6) & a_blue(s1) & Theme(s1,x6) & n_front(x5) & on(e1,x4) & n_stage(x4) & Theme(e1,x3) & Actor(e1,x2) & v_play(e1) & n_instrument(x3) & (x1 = x2) & n_people(x1))
exists e1 x1 x2.(at(e1,x2) & n_party(x2) & Actor(e1,x1) & v_perform(e1) & n_band(x1))