Powell was perhaps the first pianist to vocalize on the piano, meaning that he transfered his vocalized improvisations directly through his hands to the instrument. This gave his music a deep connection to time, which is an artifact of the human voice. Previously, horn players were more likely to express their improvisations vocally, as the mouth and breath are directly tied to the performance of horn players.
Powell suffered from Bi-Polar Disorder, and in November 1947, Powell was admitted to Creedmoor Psychiatric Center, where he stayed for more than a year, receiving electroconvulsive therapy which caused severe memory loss. The young Jackie McLean and Sonny Rollins became friends with Powell on his release from the hospital, and Powell recommended McLean to Miles Davis. However, Powell suffered from mental illness throughout his life, and had a reputation for his strange behaviour. Although his illness was almost certainly a key driver of his immense creative talent.