Why Should Repeated Melody Notes Not All Sound the Same?

When a melody repeats the same pitch several times, the fingers can easily turn it into copies of one action: similar force, duration and attack on every note. The pitches may all be correct, yet the line can sound as if it has stopped moving. “Same pitch” only identifies the key; it does not mean that each note has the same musical function.

Imagine four crotchet Gs in the right hand. The first enters after a rest, the second falls on a weaker beat, the third coincides with growing harmonic tension, and the fourth leads the phrase towards resolution. The hand must restrike the key each time, but the ear should follow one line: where it begins, continues, leans forward and settles. This need not become an obvious staircase of dynamics. Full note values, the firmness of each attack and the balance of the accompaniment can all determine whether the direction is heard.

Practise by singing the four notes as one phrase rather than four points, then preserve the same breath and destination at the piano. Add the accompaniment and check whether metre and harmony still govern the repeated notes. If every note receives an isolated accent, the problem is often not a lack of expression but attention that ends at each attack instead of hearing how one sound enters the next.

The aim, then, is not to make four physical actions absolutely identical. It is to make reliable actions serve musical positions that are not identical. Repetition on the page often asks the performer to hear change.

https://musictheory.pugetsound.edu/mt21c/MelodicAnalysis.html