What would a 5th-6th century learned Latin pronunciation have sounded like?

Question

Is there any information on the status of learned pronunciations from the late imperial period up to 1000 CE? I am wondering because the Classical Latin reconstruction seems to make clear that by the imperial period, final /m/ was regularly lost and replaced with nasalization on the previous vowel, and then of course there are the near-close short vowel allophones [ɪ] and [ʊ] for /i/ and /u/. But while in Vulgar Latin the graphic omission of 'm' indicates the lost of nasalization, and the 'e/i' 'o/u' confusion indicates the vowel mergers, later medieval Ecclesiastical Latin seems to follow a learned spelling pronunciation according to the local Romance dialect, restoring the consonantal status of final /m/ and pronouncing former short vowels the same as their former long counterparts, so [ɪ] and [iː] > [i] and [ʊ] and [uː] > [u] instead of [ɪ] > [e], [iː] > [i] and [ʊ] > [o] and [uː] > [u] in VL.

I presume that learned speakers would have followed the general patterns of most other VL./Proto-Romance consonant developments, so pre-palatal /k/ > /tʃ/ or /ts/, /g/ > /dʒ/, lost of /h/, etc. But my problem is, when would the restoration of spelling pronunciations for vowels that we see in medieval Latin––like final /m/, near-close vowel elimination, etc.––have taken place? For example, while a Classical Latin speaker would have pronounced ad dominum as [ad ˈdɔmɪnũː] would Jerome or Boethius have already said [ad ˈdɔminum], as in later ecclesiastical Latin, while their contemporary Vulgar Latin/Proto-Romance speakers would have probably said something like [a ˈdɔmnu] or [a ̍dɔmno]?

Answer 1

Long comment:

By the fifth century you'd already have this, this, this.

Palatalization of "c" before "e" or "i" would still be under way.

I'm not totally sure but "ae" and "oe" might have remained [ae̯] and [oe̯] until after the Fall of the Empire, because it seems that graphically they were replaced by "e" only around the XI century - in contrast the archaic spellings "ai" and "oi" were replaced by "ae" and "oe", reflecting a standardized pronunciation change, at the beginning of the II century AD.

Assibilation of "ti" before vowel was likely established, judging from II and III century epigraphic forms.

I hope this will narrow down the scope of your question so that someone might deal with the remaining points.

Note: Since Romance languages didn't reacquire the final "m", which was already lost in Classical Latin, it wouldn't really make sense for it to reappear in-between. This ought to be a Church Latin phaenomenon.

Answer 2

We can judge some features of educated Late Latin from the Appendix Probi (probably from the 3rd or 4th century). It is a list of corrected errors. There are can see that learned speech was different from the popular usage.

So at that time we already see indications that standard Late Latin had the same qualities for long and short vowels ("turma non torma"), pronounced classical nasal N and M like consonants ("ansa non asa", "idem non ide"), kept the Hs ("hostiae non ostiae"), avoid the merger between B and V ("bravium non brabium") and tried to keep the vowels that were disappearing in common speech ("oculus non oclus"). More than that, we already have evidence that PH was pronounced as F ("amfora non ampora").

But the Appendix Probi is not the only document were the Late Latin speakers talked about what was considered correct pronunciation. In fact, we have the words of Agustine of Hippo in his Confessions (chapter XVIII) stating that educated speakers used to care so much about the letter H that "if he who practices or teaches the established rules of pronunciation should speak without aspirating the first syllable of 'hominem', he will offend men more than if he, a human being, were to hate another human being contrary to thy (God's) commandments".

The assibilated pronunciation of C and G (that is /tʃ/ and /dʒ/) probably didn't exist until the 5th or 6th century, but from my point of view there was already some kind of palatization (maybe /c/ and /ɟ/, and that might explain how G got confused with J in Proto-Romance). The palatization of T (as /ts/) and D (as /dz/) before /j/ was already considered standard by grammarians like Pompeius in the 5th century.