How fascinating it would be to know exactly how Chaucer spoke, or Shakespeare, or even Dr Johnson. In the 21st century we have growing evidence of change in pronunciation as records of different regional and class speech accumulate. Even cinema provides examples. Laurence Olivier's film about the hesitating Prince of Denmark seems to be about "Hemlet", manifesting an upper-class vowel-flattening that has gone out of fashion even for the Queen (compare her early broadcasts with today's). But it's unlikely that anyone ever spoke off-screen in an Elstree Studios, "Lawks-a-mussy" cockney.
A recent change in everyday speech is the adoption of the American shopping mall, pronounced "mawl", unlike our traditional route to Buckingham Palace, which still has a short "a". There's also a fashion for Frenchified versions (via America) of "homage" and "herb", which sometimes now lose their initial "h" in pronunciation, with "homage" getting a long second syllable to rhyme with "marge". On the other hand, there is no sign of a return to "an 'otel" or "'umour", although, for all I know, both still ricochet off the walls of the Athenaeum.
"Covert" now rhymes with "overt" (instead of beginning with the same vowel sound as in "glove"), and "aristocrat" often has the stress on the second syllable, as preferred in the US (and some parts of the UK).
The BBC used to be our guide in matters of controversy, until where to put the stress in that very word became controversial. But at least its archive will be of increasing value and interest as the years go by.
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