A singer of a band on stage.
A singer is on stage.
Bands usually have a lead singer.
exists x1 x2 x3.(a_topic(x1) & of(x1,x2) & on(x2,x3) & n_stage(x3) & n_band(x2) & n_singer(x1))
exists p1 x1.(exists x2.(on(x1,x2) & n_stage(x2)) & n_singer(x1))