Olivier Messiaen
Messiaen said of himself that he was a “composer and rhythmician”.  He meant by this that rhythm was very important in his music.  He taught himself all about Greek metres although he did not speak the Greek language.  He liked rhythms which use odd numbers.  Very often a bar of his music may have one extra semiquaver so that there might be 17 semiquavers in a bar.  He studied Hindu rhythms and found ways of changing the rhythms during the music.  He was very influenced by the rhythms in  Stravinsky’s famous piece The Rite of Spring.