A mid sized mixed gender choir sings while the director motions to keep beat.
A choir is preparing for a concert.
Sentence 1 does not state that the choir is preparing for a concert, the first sentence just talks about presently singing and the director not the context in how it is occurring.
(-x)
exists e1 x1 x2.(for(e1,x2) & n_concert(x2) & Actor(e1,x1) & v_prepare(e1) & n_choir(x1))