A brown-haired male singing while playing a guitar.
A man busks in a subway.
A person can be singing and playing a guitar in many places not just in a subway.
exists e2 e1 s1 x1 x2 x3.(a_topic(x1) & while(e1,e2) & Theme(e2,x3) & Actor(e2,x2) & v_play(e2) & n_guitar(x3) & Actor(e1,x2) & v_sing(e1) & (x1 = x2) & n_male(x1) & a_brown-haired(s1) & Theme(s1,x1))
exists x1 x2 x3.(a_topic(x1) & in(x1,x3) & n_subway(x3) & n_busk(x1) & of(x1,x2) & n_man(x2))