Guitarist and drummer on stage at a concert.
The musician stand on stage during a concert
Presumably, musicians, not musician. And the the guitarist and drummer would be considered as musicians.
exists s1 x1 x2 x3 x4.(ne_nam_guitarist(x1) & a_topic(s1) & subset_of(x2,s1) & on(x2,x3) & at(x3,x4) & n_concert(x4) & n_stage(x3) & n_drummer(x2) & subset_of(x1,s1))
exists s1 x1 x2 x3.(n_stand(x1) & a_musician(s1) & Theme(s1,x1) & a_topic(x1) & on(x1,x2) & during(x2,x3) & n_concert(x3) & n_stage(x2))