It was composed by Monk in honor of his friend, fellow pianist Bud Powell, and based in part on the Irving Berlin standard "Blue Skies".
"In Walked Bud" was based on the chord progression of "Blue Skies", an early pop standard composed in 1927 by Irving Berlin.
According to this account, Powell was struck in the head by a police officer with a nightstick, suffering an injury that led to a pattern of institutionalizations and destructive behavior that plagued the rest of his career.
Other sources have explained Powell's injury differently; Miles Davis said Powell was beaten by a Savoy Ballroom bouncer after walking in the club without any money, while Dexter Gordon claimed he was beaten while in police custody after his arrest for drunk and disorderly conduct in a Philadelphia train station.
[3] Monk recorded "In Walked Bud" several times during his career, starting with the 1947 sessions later compiled for Genius of Modern Music (1951).