These people are demonstrating for their leader.
The leader is singing a song and playing ping pong.
Demonstrations for leaders do not happen while the leaders are playing ping pong.
exists e1 x1 x2.(n_leader(x2) & of(x2,x1) & n_thing(x1) & n_people(x1) & for(e1,x2) & Actor(e1,x1) & v_demonstrate(e1))
exists e2 e1 x1 x2 x3 x4.(n_leader(x1) & Theme(e2,x3) & Actor(e2,x1) & v_play(e2) & n_pong(x3) & of(x3,x4) & n_ping(x4) & Theme(e1,x2) & Actor(e1,x1) & v_sing(e1) & n_song(x2))