A guitar band is playing on stage.
A guitar band is playing well.
Just because a guitar band is playing well doesn't mean they're on stage.
exists e1 x1 x2 x3.(on(e1,x3) & n_stage(x3) & Actor(e1,x1) & v_play(e1) & n_band(x1) & of(x1,x2) & n_guitar(x2))
exists e1 s1 x1 x2.(a_well(s1) & Manner(e1,s1) & Actor(e1,x1) & v_play(e1) & n_band(x1) & of(x1,x2) & n_guitar(x2))