People singing and dancing.
Some people sing and dance.
singing and dancing are the same as sing and dance, just different tenses.
exists e2 e1 x1 x2.(Actor(e2,x2) & v_dance(e2) & n_people(x2) & Actor(e1,x1) & v_sing(e1) & n_people(x1))
exists e1 x1 x2.(Theme(e1,x2) & Actor(e1,x1) & v_sing(e1) & n_dance(x2) & n_people(x1))