/e 'luʧəvæn le 'stele/

These are indeed trying times, and made none the less trying by the mispronunciation called out in my subject. I don't know either why this is so painful or why people do it. Puccini has spelled it out in the first four words of the aria....

<aside type="boogy-woogy">
I mean, it's not like, say, Squeeze's Up the junction, where the name of the song is not mentioned until the last line. (Not sure why that occurred to me.)
</aside>

... with stress obviously, clearly, musically on the second syllable of lucevan. And the orchestration is as sparing as can be; the tenor is as clear as... [ed. can you do something with "bell/bel canto" here?] [You'll be lucky sunshine.]...a very clear thing.

The words are there, spelled out, what possible excuse is there for mangling the Italian? But the DJ on Classic FM (it would be invidious [indeed pointless] to name him, but he's an educated chap) says 'Here it is from Tosca, E loochevan le stele'.  Strange that he doesn't pick up the obvious clues; it doesn't take a great linguistic gift to hear something so simple.

Another frequent trial [while we're on the subject of bees in bonnets] comes for the Classic FM listener (or, more regularly except in these days of isolation, for a choral singer) whenever an r closes a Latin syllable. In English (in RP, that is) an r in this position does something strange to a preceding vowel (a bewildering array of strange things ...

<plug>
In due course ...

<really_though>
[hollow laugh; breath retention is not advised]
</really_though>

... WVGT2bk will list these. But its tortoise like progress has already covered most r words; only UR to go. AR, for example, can represent /ɑ:/ (in par), /eə/ (in pare), /ær/ (in parry), /ᴐ:/ (in war),  /ər/ (in parietal),  /ɒr/ (in quarry)... to list only the obvious cases. The whole grisly story (grisly, that is, for students of ESOL) is covered for AR, ER, IR, and OR words in WVGTbk2 , which will be free to download over the Easter weekend.</plug>

) Anyway, that frequent trial. The life of a choral singer is beset by fellow singers who – when singing Mozart's sublime Ave Verum Corpus, for example – insist on pronouncing the last word as if it were some kind of regimental mascot ("corps puss", geddit? [bou-boum tsh].)

That's all for now; the great outdoors is calling...

b

Update 2020.04.10.17:40 – Added PS

PS A similar mistake  happens with  Che gelida manina. The words are the first thing you hear after an unfussy introduction, and all clearly enunciated on one note. In Lucevan le stelle, the one note statement comes after the clarinet's I left my love in Avalon tune. In Che gelida manina, though, the mangling of the stress is subtly different. Whereas Lucevan is stressed (correctly) on the second syllable, gelida is stressed on the first.

<mnemonic type="approximately homophonic, irreverent">
Think of "jellied eels" – long-short-short.
</mnemonic>

So I ask myself again why the mis-stressed version (gelida) is so common. There's no excuse; the right stress is there, spelled out in the music.