Clavichord, clavicytherium, virginal, celesta. The one clavichord I've played was very quiet. The celesta doesn't have strings -- the hammers strike tuned pieces of metal. Sort of like a music box with more range and a keyboard.

There's also a type of hammered dulcimer called the "piano dulcimer" because the notes are linear and in the same pattern as the black and white keys on a keyboard.