Whenever the band performed, Duke took his role as the piano player seriously. He had no problem playing as a member of the rhythm section. Duke didn't play chords as much as he played colors and this had a profound effect on who ever was soloing.
His use of color tones, sometimes outside the key was a staple of what Billy Strayhorn called the "Ellington effect". Those sounds are still a mystery to many musicians. The following performance of "All Too Soon" is wonderful example of this.
Musical stimulation was Duke's goal every time he sat down to play. He rarely indulged in empty soloing. What he did indulge was his capacity to take the music he was performing to a different place. Many of his solos also contained the germs of new compositions. Sort of a preview into the sorcerer's mind.
Duke's music is still being played, studied and discussed and that alone is a tribute to this stride piano player who was... "Beyond Category".
The groove continues....