Simplify the following text for a Grade 12 native English-speaking person.
Original: In 1920 the orchestra hired Henry Hadley as `` associate conductor '' given specific responsibility for the `` Americanization '' of the orchestra : each of Hadley 's concerts featured at least one work by an American-born composer .
Simplified: In 1920 the orchestra hired Henry Hadley as `` associate conductor '' to perform concerts which included works by American composers .