Simplify the following text for a Grade 7 native English-speaking person.
Original: In the Adagio of his Symphony No. 9 a solo bassoon interpolation following the main theme appears first in D minor , returning twice more notated in C minor .
Simplified: In the Adagio of his Symphony No. 9 a solo bassoon theme appears first in D minor , but comes back two more times notated in C minor .