I think the music speaks for itself. (…)
Monk’s distinctive sound, his approach to the piano, was deliberate, very thought-out. It was hard for Monk to play Monk, in fact. (,,,) But about those wrong notes: Monk’s radical idea was not to add more notes to chords but rather take them away, creating much more dissonance. He’d often play two-note chords—for instance taking the third and the fifth out of a major seventh chord and playing just the root and major seventh—and wham, there’s Monk’s sound. It’s the right chord, yet he makes it sound like a completely bizarre choice.
from an interview by Douglas Gourney to Robin D. G. Kelley, author of Thelonious Monk: The Life and Times of an American Original