Though a keyboard instrument like the piano and harpsichord, the clavichord created the sound by striking the strings (like the piano) with a metal ‘tangent’ similar to the head of a screw-driver. This gives it it’s characteristic metal sound compared with the warmer sound created when a soft felted hammer strikes a piano string. Other differences were that the strings of a clavichord were laid parallel to the keyboard compared with the piano and harpsichord, whose strings were laid perpendicular to the keyboard.
