Simplify the following text for a Grade 8 native English-speaking person.
Original: During the 1930s , his career as a conductor took off with his appointment with the Vic-Wells ballet ( later The Royal Ballet ) , but his career as a composer stagnated .
Simplified: During the 1930s he performed a lot as a conductor with the Vic-Wells ballet ( later the Royal Ballet ) , but he stopped composing music .