Young adults are playing musical instruments.
These people are having fun
Young adults playing musical instruments does not necessarily imply they are having fun.
exists e1 s1 s2 x1 x2.(Theme(e1,x2) & Actor(e1,x1) & v_play(e1) & n_instrument(x2) & a_musical(s2) & Theme(s2,x2) & n_adult(x1) & a_young(s1) & Theme(s1,x1))
exists e1 x1 x2.(n_people(x1) & Theme(e1,x2) & Actor(e1,x1) & v_have(e1) & n_fun(x2))