Bach used the clavichord as a standard tool for teaching his students a "sensitive touch".
While "clavier" is a general term for keyboards, many scholars believe the unfretted clavichord was a primary inspiration for these preludes and fugues. Bach_Clavichord.rar
Historical records and modern recordings—such as those found on Internet Archive or performed by artists like András Schiff —frequently feature the following: Bach used the clavichord as a standard tool
His first biographer, Forkel, noted that the clavichord was Bach's preferred keyboard instrument for practice. András Schiff Plays Bach on the Clavichord Bach_Clavichord.rar
It is the only historical keyboard where the player's finger remains in direct contact with the string via a metal tangent, allowing for expressive nuances like volume control and pitch bending.