Simplify the following text for a Grade 9 native English-speaking person.
Original: He entered the Paris Conservatoire in 1904 , where he studied with Louis DiÃ mer and Lazare LÃ vy ( piano ) , Alexandre Guilmant and Louis Vierne ( organ ) , and Charles-Marie Widor ( fugue and composition ) .
Simplified: He entered the Paris Conservatoire in 1904 , where he studied the piano and organ . His organ teachers were the most famous organists in France : Alexandre Guilmant and Louis Vierne , and also Charles-Marie Widor who taught him how to compose .