Hipster performs on the acoustic guitar.
a thrash metal concert plays behind a boy in a fancy hat
A hipster is not necessarily always a boy and does not necessarily attend a thrash metal concert.  Performs implies that the hipster is performing; whereas plays behind a boy implies the boy is attending or listening to a concert.
exists e1 s1 x1 x2.(n_guitar(x2) & a_acoustic(s1) & Theme(s1,x2) & ne_nam_hipster(x1) & on(e1,x2) & Actor(e1,x1) & v_perform(e1))
exists e1 s1 s2 x1 x2 x3 x4.(behind(e1,x3) & in(x3,x4) & n_hat(x4) & a_fancy(s2) & Theme(s2,x4) & n_boy(x3) & Actor(e1,x1) & v_play(e1) & n_concert(x1) & of(x1,x2) & n_metal(x2) & a_thrash(s1) & Theme(s1,x1))