The art of expressing it is a way in which the notes of the chords are distributed or spaced. When you listen to music, you probably focus on the melody. That is the familiar part of a melody that is easy to hear.
When you sing or hum part of the music, it is the melody and not the background that you think about. For this important part of the music to stand out, the melody must be louder than the accompaniment. However, this is not always easy to do.
Each voice should flow smoothly into the next and your hands will most likely move just a little. By voicing chords, you draw attention to certain notes more than others. So sometimes, instead of using a clear melody, artists play a bunch of double notes and chords. You should always express all double notes and chords to give them more clarity.
If you play all the notes at the same volume, you will not be able to hear the melody very clearly. So you’ll want to select a note in each chord to play a little louder. This is what we mean by expressing.
If your hands are jumping all over the place, you are probably not using a good voice direction. The art of directing the voice is the smooth movement of notes from one chord to the next. Very often the note you need to express is at the top of the chord, but sometimes the middle voices have hidden melodies that are more interesting than the top voice.
When looking at a chord passage in your music, decide which voice needs more sound and which can be played softer. Listen to other recordings of pianists that highlight the top voice of each chord in the right hand.
With practice, try playing the middle note of a chord louder than the other two notes. Next, focus on the bottom note of a chord. Think of the chords that are sung in a choir. Each note is a different voice such as bass, tenor, alto, and soprano. Your ear will generally hear the soprano sing and follow the melody line. Those wonderful harmony parts add a lot of color, flavor and tone to the background of the song.
The voices become easier to play and you will find that your hands hardly move, especially when it comes to shell voices, as the roots move down in fifths or up in fourths. Later you will learn more bebop-style left-hand voices, unrooted left-hand voices, and unrooted shell voices. When the left hand plays the third and seventh of each chord, these uprooted voices give the right hand the freedom to improvise.