piano action

nouns

action consisting of a system of levers that move a felt hammer to strike the strings when a key is depressed
piano action
is a part of
a keyboard instrument that is played by depressing keys that cause hammers to strike tuned strings and produce sounds
forte-piano, piano, pianoforte
is a type of (narrower)
the operating part that transmits power to a mechanism
"the piano had a very stiff action"
action, action mechanism