Simplify the following text for a Grade 9 native English-speaking person.
Original: Working in the bebop and hard bop idioms early in his career , Coltrane helped pioneer the use of modes in jazz and later was at the forefront of free jazz .
Simplified: Coltrane played the bebop and hard bop styles of jazz early in his career , and helped start the use of modes in jazz and later was a very important part of free jazz .