A young man plays a bass guitar on stage with a another young man playing drums in the background.
the young man wrote the song
A young man may not have been who wrote the song.  The young men may not be playing a song.
exists e1 e2 s1 s2 x1 x2 x3 x4 x5 x6 x7 x8.(n_background(x8) & with(e1,x5) & in(e2,x8) & Theme(e2,x7) & Actor(e2,x6) & v_play(e2) & n_drum(x7) & (x5 = x6) & n_man(x5) & a_young(s2) & Theme(s2,x5) & on(e1,x4) & n_stage(x4) & Theme(e1,x2) & Actor(e1,x1) & v_play(e1) & n_guitar(x2) & of(x2,x3) & n_bass(x3) & n_man(x1) & a_young(s1) & Theme(s1,x1))
exists e1 s1 x1 x2.(n_song(x2) & n_man(x1) & a_young(s1) & Theme(s1,x1) & Theme(e1,x2) & Actor(e1,x1) & v_write(e1))