Harpsichord by Alan Gotto, 2015, Norwich, UK
After Anonymous, 1667, Paris, now in the Museum of Fine Arts, Boston.
Single Manual, GG/BB-c’’’, 2×8’, with short and broken octave (Split CC# and DD# keys with front halves sounding AA & BB)
The short octave set-up is where the note that appears to be low BB actually sounds GG.
The broken octave set-up is directly-related to the short-octave set up. As you probably have noticed, a short-octave set-up means the low notes, CC# and EEb are not available since they are tuned to AA and BB. A broken octave set-up was often added to the short -octave to over come this problem. The CC# and EEb keys would be split, or broken in half, into two keys. The back halves of each key sound CC# and EEb and the front halves sound AA and BB, as show in the picture of my instrument above.
Physical Harpsichord Technique Implications
The short and broken octave bass gives one a sense of “magic” in playing low bass notes in octaves (GG, AA, BB) since your hand hardly has to expand to play the notes. But an even greater sense of magic comes when you play works of Louis Couperin, Chambonnières or D’Anglebert, which call for chord intervals in the bass of a 12th, such as AA-E (Louis Couperin, Allemande in D-major, No. 58, m. 20, Moroney edition). These passages in fact require a short octave bass-setup — they are not playable on later harpsichords as written with a chromatic bass.