How does tempo rubato alter timing while preserving an underlying beat?

Tempo rubato, meaning "robbed time," is a technique of subtle rhythmic manipulation where a performer intentionally deviates from a strict tempo for expressive purposes.12

The technique alters timing by stretching or compacting specific beats, measures, or phrases. To preserve the underlying beat, the performer must treat the steady pulse as a necessary framework; the music departs from this inflexible beat but must eventually return to it. While the performer may speed up or slow down to add character—such as tautening the tempo in a loosely knit passage or slackening it in a crowded one—the written note values are not disregarded.12

Ultimately, rubato relies on the tension between the fluid, expressive performance and the listener's awareness of the steady, underlying pulse.23