Singers performing to the crowd.
Musicians are playing music.
When a singer is performing they are not considered musicians.
exists e1 x1 x2 x3.(n_crowd(x3) & a_topic(x1) & to(e1,x3) & Actor(e1,x2) & v_perform(e1) & (x1 = x2) & n_singer(x1))
exists e1 x1 x2.(ne_nam_musicians(x1) & Theme(e1,x2) & Actor(e1,x1) & v_play(e1) & n_music(x2))