Simplify the following text for a Grade 9 native English-speaking person.
Original: Copland 's Music for the Theatre ( 1925 ) and the Piano Concerto ( 1926 ) were both composed for Koussevitzky .
Simplified: Koussevitzky led the orchestra for the first performance of Copland 's early work , `` Music for the Theater '' , in 1925 . Koussevitzky also conducted Copland 's `` Concerto for Piano and Orchestra '' in 1927 .