Brunette woman is signing while playing a piano.
A woman in the choir plays piano.
Just because she plays an instrument doesn't mean she is in a choir.
exists e2 e1 x1 x2 x3.(while(e1,e2) & Theme(e2,x3) & Actor(e2,x1) & v_play(e2) & n_piano(x3) & Actor(e1,x1) & v_sign(e1) & n_woman(x1) & (x1 = x2) & ne_nam_brunette(x2))
exists e1 x1 x2 x3.(n_choir(x2) & Theme(e1,x3) & Actor(e1,x1) & v_play(e1) & n_piano(x3) & in(x1,x2) & n_woman(x1))