From the time of Renaissance, the sound of pipe organ must have been very important part of life.
This pipe organ sound and tuning system must have given a great influence to the composers.

From 17th century to early 18th century, Baroque is the Golden age of pipe organ.
Bach was also a great organist in this period.  He must have full knowledge of characteristic of this instrument.

Transition of Classical Temperament from Pipe organ to Modern Piano
Early Renaissance: Mean tone tuning system
Middle Renaissance: Tuning system of Praetorius
Baroque: Tuning system of Schnitger
Bach’s tuning system: From Bach’s Seal and scroll design of WTC( Das Wohltemperirte Clavier)
Tuning system for modern piano: Arranged from Bach’s Seal

These have common characteristics.  In order to see the transition clearly,
Please click the file Windows Media Video.
Transition of Classical Temperament from Pipe organ to Modern Piano.
( Between Schnitger and Bach/WTC, there is another tuning system which I feel very important. )

explanation of video:
There is a “wolf” in meantone. This is a wide 5th.
You can see this trace in tuning system of Praetorius and Schnitger.
Also the trace of wolf could be seen in the beautiful placement of major 3rd of Bach’s tuning system, from decipherment of Emile Jobin.
From his analysis, Bach gave up a perfect pure 3rd, 5th is not wide anymore, but beautiful 3rd still remains from the meantone.
Bach’s Seal tuning system is very favarable system, but it does not the fit the modern piano which is in strong inharmonicity.

Like that of Very Well 1.0, when Bach’sSeal 1.5 and Bach’s Seal 1.0 is arranged for modern piano, the tonality remains and if will fit modern piano.

 
Chisako Murakami translated it into English from pianotuning.jp
Special thanks to Ms. Midori Kita.