The instrument with a 61-key keyboard that is frequently used in classical music is the piano. This versatile instrument produces sound by striking strings with hammers when keys are pressed, allowing for a wide range of dynamics and expression. Pianos come in various types, including grand and upright, with varying sizes, tonal qualities, and uses. In classical music, the piano plays a significant role, serving as a solo instrument and an accompaniment for singers and other instruments. Renowned composers, such as Beethoven, Chopin, and Mozart, have written extensively for the piano, contributing to its rich repertoire.