Phonology of Voynichese

[Koen G]

It's a correct remark that Medieval texts were meant to be voiced out. Popular belief has it that many readers were even unable to read without saying or at least mouthing the words at the same time.

There's the among linguists well-known anecdote from Augustine about his mentor Ambrosius:

"When Ambrose read, his eyes ran over the columns of writing and his heart searched out the meaning, but his voice and his tongue were at rest. Often when I was present—for he did not close his door to anyone and it was customary to come in unannounced—I have seen him reading silently, never in fact otherwise. I would sit for a long time in silence, not daring to disturb someone so deep in thought, and then go on my way. I asked myself why he read in this way. Was it that he did not wish to be interrupted in those rare moments he found to refresh his mind and rest from the tumult of others' affairs? Or perhaps he was worried that he would have to explain obscurities in the text to some eager listener, or discuss other difficult problems? For he would thereby lose time and be prevented from reading as much as he had planned. But the preservation of his voice, which easily became hoarse, may well have been the true cause of his silent reading."

Agustine was perplexed by Ambrose's ability to read in silence. In fact he tried to emulate the skill, but only got to the point where he was silently mouthing along with the text as he read. That is to say, for the (early) medieval reader, text and sound were one. I'm not entirely sure if this had evolved much by the 15th century. 

This is, in my opinion, an argument against overly complex ciphers, so worthwhile to point out. 
I don't know how it will help us further though. Aren't we still in the situation where we try to guess sound values for glyphs, as we've been for a hundred years?