Exactly! It did not. C major was favourite in Medieval times. The whole psalm related to the phonetic naming of the 7 (out of 12) notes as syllables happened to be in C major ("natural).gaggle of hermits wrote: Tue Jan 04, 2022 11:19 am what makes you think instruments, such as the hydraulis, built at a time when the main system in use was based on a set of tetrachords and separating tones bounded by A at each end would favour C major as the primary scale?
Yet, the letter assignment of the notes did not start with Ut = A, Re = B, Mi = C.
A is La most likely because of (I am speculating because I was not there) a misconception about the old naming of intervals done by Boethius, and A was assigned to the key on the most left (of the clavichords at that time).
In short: it is just a mess!