These people are standing on a stage, singing and waiving flags.
A group of performers are on stage.
People don't have to be performers to stand on a stage.
exists e1 e2 e3 x1 x2 x3 x4.(n_people(x1) & for(e1,e3) & Theme(e3,x4) & Actor(e3,x1) & v_waive(e3) & n_flag(x4) & for(e1,e2) & Theme(e2,x3) & Actor(e2,x1) & v_sing(e2) & n_flag(x3) & on(e1,x2) & n_stage(x2) & Actor(e1,x1) & v_stand(e1))
exists p1 x1 x2.(exists x3.(on(x1,x3) & n_stage(x3)) & of(x1,x2) & n_performer(x2) & n_group(x1))