A man is playing the guitar while another man is playing the drums behind him.
The men are in a band.
Just because they are playing instruments doesn't mean they're in a band.
exists e1 p1 x1 x2 x4.(n_male(x2) & n_drum(x4) & n_guitar(x2) & exists e2 x3.(behind(e2,x2) & Theme(e2,x4) & Actor(e2,x3) & v_play(e2) & n_man(x3) & -(x3 = x1)) & n_man(x1) & n_man(x1) & while(e1,p1) & Theme(e1,x2) & Actor(e1,x1) & v_play(e1))
exists p1 x1.(n_man(x1) & exists x2.(in(x1,x2) & n_band(x2)))