The strings in clavichords vibrate from the bridge to the tangent (the metal hammer that strikes the string), the remaining distance to the tuning peg is covere

The strings in clavichords vibrate from the bridge to the tangent (the metal hammer that strikes the string), the remaining distance to the tuning peg is covered in damping felt and so does not contribute to the sound. On a "fretted" clavichord, several notes strike the same course (of two strings) at different positions. Only one note can play at a time on each course, so some combinations of notes aren't possible. Unfretted clavichords have a course for each note, but weren't at all common in J.S. Bach's time.