Simplify the following text for a Grade 6 native English-speaking person.
Original: At age 17 , upon moving to Paris , he took private organ lessons with Charles Tournemire , whom he assisted at Basilique Ste-Clotilde , Paris until 1927 .
Simplified: When he was 17 he went to Paris and had private organ lessons with Charles Tournemire . He became Tournemireâ s assistant at the Basilique Ste-Clotilde , Paris until 1927 .