Interesting to read that Bernstein was a member of the Communist Party. As someone who's studied music and been a fan of Bernstein for years, I've not once heard this, despite having read quite a bit about his music.
His politics has been whitewashed so hard it's not funny, and it's never mentioned when his music is discussed.
Another excellent book on this subject, which examines Bach's counterpoint and its varied meanings to his contemporary society, including religious meanings, is "Bach and the meanings of counterpoint" by David Yearsley. A terrific read full of examples for those interested.
There are some basic errors, too, which are in the overarching structure of linguistic categories. For instance, 'and' is _not_ a preposition, as it states that it is in the language grammar sections.
Perhaps this is a curmudgeonly and pedantic observation, but linguists be linguists.
Your pointing to the Papal States reminds me: another period of Italy's history also demonstrates this narrative quite well. The Fascist government was the first body to publish a large amount of literature in Italian, which lead to more Italians speaking it than ever had. And as the people used Italian as a kind of pidgin under the Papal States, so too did they use it as a pidgin when so many were displaced during and following the War and the partisan resistance.
Something that isn't directly addressed in this article is the astonishing fact that, despite Dante's having written seven centuries ago, Italians can still (with some difficulty) understand what is meant when they read his writings (at least, those in vernacular). Such is the influence of Dante's literary language on the language of ordinary Italians today.
To put this into perspective, Chaucer was two generations after Dante, and his writings are _barely_ comprehensible by layreaders. Here's a bit of the prologue of The Canterbury Tales:
And specially from every shires ende/
Of Engelond, to Caunterbury they wende,/
The hooly blisful martir for to seke/
That hem hath holpen, whan that they were seeke.
His politics has been whitewashed so hard it's not funny, and it's never mentioned when his music is discussed.