The Erlangen treatise dates from 1430 – 1450 and gives two different descriptions on how to set tangents on a clavichord. It results in a very interesting modified Pythagorean tuning with pure thirds in central keys. Taking the outline from Arnault and the positions for the tangents from a Erlangen treatise I got a perfect instrument for 15th century music.
Pitched at 4' pitch this instrument with a range from B-f'' plays all the music until around 1520, when for the first time lower notes are required.
Interesting about the tuning is also, that it is very similar to the system Kirnberger asks for in 1766. These Pythagorean tunings fulfilled the needs of composers for over 300 years, while mean-tone had its brief episode only.
This little compact instrument is a favorite of mine. It fits the bottom of my suitcase and I take it with me to have a keyboard instrument in hotel rooms. And I use it to make up my own intavolations from Josquin's music, sight reading through his vocal repertoire, trying to play all the lines. Then I feel like being at home with my favorite composer playing house music.
And it leads me back to one of my first musicological teachers, Martin Vogel, how points out the fine points about these tunings in his 'Lehre von den Tonbeziehungen' from 1975.