Thelonious MONK was an American jazz pianist and composer. He is widely considered one of the most influential jazz musicians of the 20th century, and his unique style of playing has been described as a mix of bebop, stride, and modern jazz. MONK's compositions have become standards in the jazz repertoire, and he is remembered for his improvisational skills and his ability to create complex musical structures. He was also known for his eccentric behavior and his use of humor in his music.