Two old men play guitar and sing at a rock concert.
Two men are singing by themselves.
Two old men is allot more specific than the phrase two men, also a rock concert which implies a crowd is very different then by themselves.
exists e1 s1 x1 x2 x3 x4 x5 x6.(at(e1,x5) & n_concert(x5) & of(x5,x6) & n_rock(x6) & Theme(e1,x2) & Actor(e1,x1) & v_play(e1) & n_sing(x4) & n_guitar(x3) & subset_of(x4,x2) & subset_of(x3,x2) & n_man(x1) & a_old(s1) & Theme(s1,x1) & card_eq_2(x1))
exists e1 x1 x2.(n_group(x2) & by(e1,x2) & Actor(e1,x1) & v_sing(e1) & n_man(x1) & card_eq_2(x1))