‘A clavichord should sound loud, but not banged, rather gentle, in the manner of a harp. It should also resonate long and pleasantly. (…) since one now like to have the bass rich and full, but the
higher octaves progressively more delicate and harp-like.’
Jacob Adlung Musica Mechanica Organoedi, 1726 (p.153)

Playing in Bach’s Manner

‘This popular instrument is every player’s first ABC so to speak, for once they are proficient on it, they can also get around the spinet, harpsichord, regal, positive,and organ’.
Johann Gottfried Walther,MusicalischesLexicon, Leipzig, 1732, p.169

Friedrich Conrad Griepenkerl published in 1819 referring to Johann Nikolaus Forkel’s publication
On J.S. Bach’s Life, Art, and Compositions Bachs Chromatische Fantasie and Fugue BWV 903.  Griepenkerl explains:

‘The mechanismof the hand is made for grasping’.

What he means is that the fingers reach towards the inside of the hand when playing. He goes on to say that the fingers should be round and curved when at rest, noting: ‘However, the unequal strength and flexibility of the fingers makes compensation necessary’. J.S. Bach found this compensation by using the weight of the hand and arm, ‘which one can either maintain in equal strength or increase and decrease with ease and at will’. And Griepenkerl concludes:

‘This intimate connection between rapid force and weight of the hand on the keys is therefore the most essential aspect of the whole principle of Bach’s keyboard manner.’