Yeah, that seems strange.
A typo in a list of pronunciations would be really hard to catch, thinking about it.
That link just presents me with the cover and “No Preview.” Google Books is cantankerous with me insisting on changing the “.com” to “.co.th” and (sometimes!) presenting Thai language despite the umpteen preference cookies I’ve set for Google. It often lets me look at books, but now I wonder if some of the other “No Preview Available” messages were due to my location. 
As a child I read a book in which uneducated people often spoke of eating “vittles”. I knew the world they meant was “victuals”, and I thought it was the author’s way of showing their ignorance. In fact, they were pronouncing it correctly!
Also, when I learned the correct “victuals” pronunciation a few years ago, I thought of an obscure Mother Goose rhyme which begins: “I knew an old woman and what do you think?/She lived upon nothing but victuals and drink.” Pronounced “vittles”, it scans better than if it were “vik-chew-uls”.
The most obvious method is simply the linguistic game of telephone. You hear a word and try to mimic it, but you don’t get it exactly right. Over time, those changes become bigger.
Written language doesn’t change as much, since you can plainly see what the word is. The period in which it did change a lot was before the printing press, and thus before most people had access to a lot of writing. So they’d just spell a word they’d learned verbally.
Now that we can both hear and see words from large distances, the changes are much slower.
Good posts in this thread. Let me just add that, often, another factor is when lots of people migrate from one region to another, and intermarry with the natives. The parents (or one of them) may subtly alter their pronunciation of certain words, to facilitate communication – and the children will internalize the new style as standard, eventually passing it on to their own children.
This is especially pronounced when the parents have different first languages, and so one of them is mispronouncing the language common to the couple (in other words, second-language interference, rather than mere first-language regional accent). If widespread, this leads to partial or deep “creolization” – that is, a simplifying of some of the language’s grammar or structure, not just pronunciation change.
(This is not the thread to discuss the debates over “simplification”…just understand that languages usually compensate for the loss of one complexity – e.g., inflections – with the rise of another – e.g., rigid word order, or else meaning-changing tonality).
(Exapno alluded to some of what I just wrote about, in his first quoted paragraph in post 11).
So, a learned spelling back-formation. Same thing happened to “doubt.”
Here’s an NBC pronunciation handbook which must be of similar vintage, given that it also shows the “FLAK sid” pronunciation for “flaccid” (link to the item as a whole), which is entirely new to me and makes me wonder what other interesting pronunciations lurk within this 1951 handbook.
And sotto voce is shown as SOHT oh VOH chay. This strongly indicates that the SAHN in the other guide was indeed a typo.
Incidentally, the British pronunciation would be SOHT oh VOH chee. Not only can’t we agree on how to pronounce our own language, we can’t agree on how to pronounce other languages which have pronunciations of their own.
This is a pet peeve of mine. No one has trouble with listen, hasten, soften, etc. Why is it so hard to say often correctly. I especially hate it when mispronounce by a singer. Horrible, ugly sound.
I think that back when populations were smaller and people didn’t typically communicate with people outside their own village, a lot of minor things that don’t have much effect today become magnified. Maybe one of the founders of a small village has a speech impediment that subsequent generations assume is the proper way to speak. Maybe some younger people decide a certain pronunciation sounds cooler and things change a certain way in one village but a different way in the village 100 miles away.
I’ve never heard that British pronunciation, and the OED doesn’t mention it.
There may be another transatlantic difference though, assuming your “OH” represents the “o” in “vote”. I would have the “o” sounds (at least the first one, and arguably all three) as the “o” in “hot”.
Item #3 is interesting–RAY-di-oh.
I suspect this was actually necessary guidance at the time; I’ve seen old movies where somebody pronounced it RAH-di-oh, or RAD-ih-oh (rhyming with patio). The first of those is pretty close to the way the word is pronounced in some European languages, so I wonder if it has anything to do with the fact that mass immigration from Europe, especially into and through NYC, was still very recent at the time.
The Cambridge Dictionary gives it as the British English pronunciation.
The Immigration Act of 1924 cut mass immigration to a tiny fraction. And why should Hollywood care how they said anything? Or even notice? If there was any influence, I could make a case for the European contingent in Hollywood. Even that seems a stretch, though.
Actually, hardly ever.
Pronunciation can change very quickly when there is no social reinforcement of the correct pronunciation:
On a personal level, I find it interesting that in Northern California I now pronounce “no” as more like “naue” instead of “noh” as I pronounced it growing up in Indiana.
Also, When I returned to visit my Indiana home after 2 years in the Washington DC area, my family had all acquired an Appalatian drawl. Huh. 
I’ve lived in Canada (Montreal) all my life and a lot of people here say “of-fen.” I do.
Good, this example was bumped. Goddamnit I’m going to keep making this funny until someone says he gets it. Also because it really is an on-topic post/new example for OP. I can hear you breathing out there…
Hardly ever?