Cittern

Does anybody know about the placement of the frets of the cittern? I was in
Vienna at the end of July and visited the collection of ancient music
instruments in the Kunsthistorisches Museum. There are several citterns
there, all of them with the same irregular pattern of straight frets. The
instrument is bigger than a flat mandolin, but smaller than a lute. This is
what I saw:

I (first fret) higher than 12-tet, close to the 2nd fret
II lower
III higher
IV in between III and V
V OK (4:3?)
VI close to VII
VII OK (3:2?)
VIII higher than 12-tet
IX and X equally distant between VIII and XI
XI lower than 12-tet
XII OK (2:1)

The most beautiful cittern in the collection for sure is by Giralomo de
Virchi (1574). According to The New Grove, the tuning of the six double
courses was: d-f-b-g-d'-e'.
I'm looking right now to find the tablature music written for this special
instrument by De Virchi's son, Paolo, in order to see what was the approach
for the intonation.
I think some clever brains on this list may already draw a conclusion from
the tuning of the open courses, combined with the rough description of the
placement of the frets...

In the same Kunsthistorisches Museum there was also a Harmonie-Hammerflügel,
by Johann Jakob Könnicke (Vienna, 1776). This instrument, presented as being
"31-tone", was played by Beethoven and Schubert. Mozart himself had one
built. It has six identical manuals with 37 keys each. Starting from the
left the first row of seven keys are marked as follows:
Key 1 : three small dots
Key 2 : three small dots
Key 3 : no mark
Key 4 : no mark
Key 5 : a bigger round dot
Key 6 : no mark
Key 7 : no mark
Than the pattern starts again, repeating until key 35. Then comes key 36 :
three small dots, and key 37 : three small dots as well. That makes one of
the six manuals. The museum doesn't give any other description how the
instrument was tuned.

--Wim Hoogewerf