Disagreement with Mozart?

["reinifrosch@xxxxxxxxxx" <reinifrosch@xxxxxxxxxx>]

Dear colleagues,

I do not seriously disagree with him, of course, but ...

For the upcoming christmas concert of our choir, I changed the text of
"Più non si trovano", K.V. 549, also known as number IV of "Sechs Nocturnos".

In bar 10, there is a chord Bb-F-C#. We intend to have our singing 
accompanied on a DX11-synthesizer in meantone tuning, 
which sounds beautiful, with the exception of the just mentioned chord. 
If one plays Bb-F-Db instead, that chord, too, sounds very well.
(In meantone tuning, Db is higher than C# by 41 cents.)

Probably Mozart assumed ET or similar. He wrote
C# and not Db, because the next Soprano note is D.

Reinhart. 

Reinhart Frosch,
Dr. phil. nat.,
r. PSI and ETH Zurich,
Sommerhaldenstr. 5B,
CH-5200 Brugg.
Phone: 0041 56 441 77 72.
Mobile: 0041 79 754 30 32.
E-mail: reinifrosch@xxxxxxxxxx .