Bill Evans is seen as the main reformer of the harmonic language of jazz piano. Evans' harmonic language was influenced by impressionist composers such as Claude Debussy and Maurice Ravel. His versions of jazz standards, as well as his own compositions, often featured thorough reharmonisations. Musical features included added tone chords, modal inflections, unconventional substitutions, and modulations.

In Evans's harmonies, the chords feature extensions like 9ths and 13ths, are laid around middle C, have smooth voice leading, and leave the root to the bassist.

One of Evans's distinctive harmonic traits is abandoning the inclusion of the root in his chords, leaving this work to the bassist, played on another beat of the measure, or just left implied. "If I am going to be sitting here playing roots, fifths and full voicings, the bass is relegated to a time machine." This idea had already been explored by Ahmad Jamal, Erroll Garner, and Red Garland. In Evans's system, the chord is expressed as a quality identity and a color. Most of Evans's harmonies feature added note chords or quartal voicings. Thus, Evans created a self-sufficient language for the left hand, a distinctive voicing, that allowed the transition from one chord to the next while hardly having to move the hand. With this technique, he created an effect of continuity in the central register of the piano.

Evans's improvisations relied heavily in motivic development, either melodically or rhythmically. Motives may be broken and recombined to form melodies. Another characteristic of Evans's style is rhythmic displacement. His melodic contours often describe arches. Other characteristics include sequenciation of melodies and transforming one motive into another. He plays with one hand in the time signature of 4/4 and the other momentarily in 3/4.

At the beginning of his career, Evans used block chords heavily. He later abandoned them in part. During an interview, Marian McPartland asked: "How do you think your playing has changed since you first started? Is it deliberate or is it just happening to change?" Bill Evans: "Well it's deliberate, ahh but I stay along the same lines…I try to get a little deeper into what I'm doing. As far as that kind of playing goes, [jazz playing rather than an earlier example where he played Waltz for Debbie without any improvisation or sense of swing], I think my left hand is a little more competent and uhh…of course I worked a lot on inner things happening like inner voices I've worked on."

At least during his late years, Evans's favorite keys to play were A and E. Evans greatly valued Bach's music, which influenced his playing style. It helped him gain good touch and finger independence. "Bach changed my hand approach to playing the piano. I used to use a lot of finger technique when I was younger, and I changed over a weight technique. Actually, if you play Bach and the voices sing at all, and sustain the way they should, you really can't play it with the wrong approach." Evans valued Bach's Well Tempered Clavier and his three-part inventions as excellent practice material.

Bill Evans' 'rootless' voicings-example

Play "Foolish Heart"

Examination of Evans' Harmony-refer to above phrases