I've recently completed writing a paper for a lecture about "The Colour of Tuning in Mozart's Time" and made some interesting discoveries.
The Mozart Fantasias written for Mechanical Organ are usually given an enjoyably muscular treatment in performance on the organ and no doubt we've all enjoyed them that way.
However, they were actually written in F minor, as most things of the period were written in F minor, on the subject of death, death of a Hero. He'd been valiant in the Battle of Belgrade and an art installation was created to commemorate his death and life, rather in the nature of what one might see at the Tate Modern. He was to be seen encased in a glass coffin, surrounded by mirrors asking for our reflection upon the scene, a mourning Turkish woman and guards, mournful, standing to attention. Surmounted by a clock, the inevitable issues of time were to come to mind, eternity, truncation of life, marching on of events, of soldiers marching.
How much of this scene does a conventional interpretation evoke, or rather if you can imagine the scene, how would a conventional interpretation add to the melancholy and to the reflection upon the sight before you?
The secret was in the tuning of the organ pipes to Meantone. Only then could the F minor evoke all the passions of
Deep depression, funereal lament, groans of misery and longing for the grave https://www.wmich.edu/mus-theo/courses/keys.html
documented by Schubart in 1787.
And the next secret was to register the performance on the ranks of pipes which would have been used by the mechanical organ of a mechanical clock.
Contemporary accounts referred to the sound of flutes and a bassoon. So a Stopped Diapason and a reed with truncated resonators, not taking up much space in the clock organ, for the bass.
The performance was said to have taken 8 minutes. https://www.youtube.com/watch?v=fJVisln4ghM
goes some way to that. But even that performance on a mechanical organ doesn't quite convey the emotion which a performance in Meantone has automatically inherent.
K608 and https://www.youtube.com/watch?v=ebKP9MiGyiI
K594 might approximate to the spirit of the originally heard performance. The interaction of the key of F minor with the temperament is essential. Kirnberger can also be used.
If performing this in this manner please refer to this post!