n. In the organ, pianoforte, and similar instruments, as the harpsichord, clavichord, etc., the series or horizontal row of finger-levers or digitals (usually called keys), by depressing which the performer causes the pipes, strings, or reeds to produce tonos.n. Pedal keyboards in the organ are called radiating when the keys are made to converge somewhat below the player's seat, like the ribs of a fan, and concave when the general level of the inner keys is lower than that of the outer ones. In the best organs the pedal keyboard is both concave and radiating.n. The set of keys for operating the letters of a type-writing or type-settingmachine.