Besides having at least a rudimentary understanding of chord progressions, it’s advantageous to be able to “sing” internally, or in full voice, as you accompany yourself through a cantabile movement.
A good example, is the Andante of the supposedly “easy” (facile) Sonata of Mozart, K. 545, which is, to the contrary, a challenge to play beautifully.
In this snippet which was sent to a SKYPE student as a supplement, I play chord blocks to my rendered treble melody, dipping or resolving at points suggested by the flow of harmony, or intensifying across measures that defy the cliche that downbeats are automatic destination points. In fact, Mozart creates an emotional twinge, as he places a vi chord on the second beat (usually weak) of two parallel measures, fleshing out the melodic G.
Her Masterclasses, especially, provide invaluable insights about phrase sculpting and contouring with direct application to piano playing.
As pianists, we are singers, too, bridging the distance between our fingers and a complex hammer mechanism–needing the broad breaths, pauses, and streams of intensity relieved by resolution.
Here, Di Donato, impeccably phrases a TRILL, which one can apply to Mozart’s ornaments in Sonata K. 545