Such as generating a spoken sentence or series of sentences in a particular person's voice?
Is it RAI for Minor Illusion to duplicate complex sounds such as speech?
and he responded with a simple "Yes".
As far as how much can be said, Josh Clark points out that in the Out of the Abyss official adventure module, an NPC uses minor illusion to simulate two senteces (p. 171).
Yes, it can
... Is exactly how Jeremy Crawford, lead rules designer of D&D 5e, answered a question on Twitter asking if Minor Illusion could produce speech. He didn't say "yes, but only..."
I see no reason why you could produce speech, but not prolonged speech. Mimicking a particular voice may require some sort of ability check, at DM discretion, but such a restriction is not in the rules, nor in official rulings from Wizards of the Coast employees.
Yes, it can
At least, Wizards of the Coast seems to think so.
In Chapter 13 of Out of the Abyss (p. 171), an NPC uses minor illusion to simulate a whole two sentences.
There's no indication of how many turns it takes, but it must be realistic sounding, because
the voice is intended to intimidate the player characters into retreating.
It might sound a tad silly, but you could use any sound and use it more or less like morse code. "I'll make a single chirp to announce you guys i casted the spell, a pause then a number of chirps equaling the number of orcs i saw, then a pause and additionnal chirps of varying intensity to convey they information about the number and potential threat of the orcs' allies"
its completely within the bound of the spell