Which term refers to 'getting faster' in a musical piece?

The term that refers to 'getting faster' in a musical piece is "stretto." In the context of music, "stretto" is often used in reference to a more rapid passage or the acceleration of tempo, especially towards the end of a section or phrase. This term is commonly applied during specific musical forms, such as in fugues, where the intensity and speed may increase, creating a sense of urgency or climax.

Understanding tempo changes is crucial in interpreting and performing musical works, as they affect the character and expression of the music. The other terms provided have different meanings and do not relate to an increase in speed. For example, "perdendosi" refers to a gradual fading away or diminishing, "meno" means 'less,' and "lieblich" denotes a gentle or sweet character, none of which imply an increase in tempo.