Simplify the following text for a Grade 7 native English-speaking person.
Original: Founded by Neville Chamberlain , the orchestra first performed as the City of Birmingham Orchestra in September 1920 , with Appleby Matthews conducting its first concert .
Simplified: The orchestra was founded in 1920 by Neville Chamberlain , the man who later became Prime Minister of the United Kingdom . At that time it was called City of Birmingham Orchestra .