Performers of Romantic music (such as Chopin) often incorporate an expressive technique that involves keeping the tempo of the accompaniment steady while slowing the melody slightly before catching up a moment later. This manipulation of the temporal flow for expressive purposes is called

Rubato.

Explanation:

The word 'rubato' is derived from the Italian word 'rubare' which means to rob or steal.' In music, the word 'rubato' is used to mean being flexible in rhythm.

Tempo rubato, in a literal sense means, stealing or robbing of time. A solo performer gets the freedom and flexibility to speed up or slow down the rhythm and not sticking to the rhythms composed by the composer.

Rubato gives a performer the freedom to shift the rhythm while keeping the tempo of the accompaniment strict to the time. Pieces of the music of Frederick Chopin are most often related to the use of rubato technique.

Thus the correct answer is rubato.