Simplify the following text for a Grade 5 native English-speaking person.
Original: In 1936 Sergei Prokofiev was commissioned by Natalya Sats and the Central Children 's Theatre in Moscow to write a new musical symphony for children .
Simplified: It is a children 's story . Prokofiev got the idea from Natalya Sats , who led the Moscow State Musical Theater for Children .