What is indicated by the term una corda?

The term "una corda" is Italian for "one string," and in the context of piano performance, it indicates the use of the soft pedal. When the una corda pedal is pressed, the piano's hammers strike fewer strings, resulting in a softer and more muted tone. This technique allows the performer to create a quieter and more delicate sound, often adding expressiveness to the music.

Other options refer to different aspects of musical performance that do not relate to the specific action of the una corda pedal. Playing loudly contrasts the softening effect of the pedal, while vibrato is a technique used for string instruments to enhance pitch and tone color, and increasing tempo pertains to the speed of the music, none of which align with the meaning of "una corda."