Who developed the essential bebop piano style?

The essential bebop piano style is closely associated with Bud Powell, who played a pivotal role in its development. Powell's approach to the piano combined intricate harmonic structures with rhythmic vitality, setting a new standard for jazz piano that emphasized improvisation and melodic invention. He introduced complex chord voicings and a percussive touch that influenced many pianists after him. His ability to blend lyrical lines with the fast-paced bebop style made him a key figure in shaping the sound of this genre.

While Thelonious Monk was also a significant contributor to jazz piano with his unique style and compositional innovations, it is Bud Powell who is often recognized as the primary architect of the bebop piano style. Charlie Parker and Dizzy Gillespie, although central to the development of bebop as a whole through their contributions on saxophone and trumpet, respectively, did not focus specifically on the piano aspect. Therefore, the emphasis on Powell's signature approach to piano makes him the correct answer.