Why, if it is n't Bilbo Baggins, playing the accordion.
It is Bilbo Baggins playing a musical instrument in the room.
An accordion is not the only musical instrument in the room that Bilbo Baggins can play.
exists x1 x2 x3 x5.(n_accordion(x5) & ne_per_baggins(x2) & (x2 = x3) & ne_per_bilbo(x3) & n_thing(x1) & (-exists e2 e1 x4.(Theme(e2,x2) & Actor(e2,x1) & v_be(e2) & Theme(e1,x5) & Actor(e1,x4) & v_play(e1) & (x2 = x4)) -> exists x6.(r_why(x6) & n_event(x6))))
exists e1 p1 s1 x1 x2 x3 x4 x5.(n_room(x3) & ne_org_baggins(x4) & (x4 = x5) & ne_org_bilbo(x5) & n_thing(x1) & for(p1,e1) & in(e1,x3) & Theme(e1,x2) & Actor(e1,x1) & v_play(e1) & n_instrument(x2) & a_musical(s1) & Theme(s1,x2) & (x1 = x4))