One of the giants of the jazz piano, Bud Powell changed the way that virtually all post-swing pianists play their instruments. He did away with the left-hand striding that had been considered essential earlier and used his left hand to state chords on an irregular basis. His right often played speedy single-note lines, essentially transforming Charlie Parker's vocabulary to the piano (although he developed parallel to "Bird"). Tragically, Bud Powell was a seriously ill genius. After being encouraged and tutored to an extent by his friend Thelonious Monk at jam sessions in the early '40s, Powell was with Cootie Williams' orchestra during 1943-1945. In a racial incident, he was beaten on the head by police; Powell never fully recovered and would suffer from bad headaches and mental breakdowns throughout the remainder of his life.