The highlight for me was seeing wax cylinders and being able to understand how they work. I encountered them last year looking into the recordings of Constantin Brailoiu and they stayed a mystery to me until now.
During the studios tour, Karl, the sound archivist (/sound engineer?) mentioned he was working on some english speech training recordings at the moment. Funny enough, that is exactly what I am currently looking into.
Turns out there are countless recordings of phonetics training. This is interesting to me. I would be interested to know if other languages also had such a dedication to its pronounciation. It definitely is not the case in Romanian.
I am thinking it might be due to the imperialist nature of the UK? There is a paragraph in Cicely Berry’s Your Voice and How to Use It where she speaks about accents and class. Although things have been slowly changing over the past few decades, it seems that the accent one spoke with was of such importance that it could even determine empleyment.
*Update: Turns out there was a time when English was more of a ‘transparent language’: when spelling would match pronunciation. Then something called The Great Vowel Shift happened, between the 14th and the 17th centuries. The 7 existing vowels turned into 12. But spelling never changed accordingly (because the printing machine had already been invented by the 17th century?). There is no clear reason for this great vowel shift, but they say it was due to Londoners (?) wishing to distinct themselves from the migrants brought from the North by the Black Death.
*William Shakespeare invented 1700 words in modern English that we still use today.
I had a look through the Sound Archive and found this recording I am thinking of using in my audio paper (I was imagining part of it sounding like an english vocal exercise):
https://sounds.bl.uk/Accents-and-dialects/Early-spoken-word-recordings/024M-1CS0011526XX-0100V0
Update: I spent a bit more time listening through the archive. I found this gem:
https://sounds.bl.uk/Accents-and-dialects/Early-spoken-word-recordings/024M-1CL0005132XX-0200V0

Definitely going in my audio paper.
Deeper, deeper, deeper, please!
https://sounds.bl.uk/Accents-and-dialects/Early-spoken-word-recordings/024M-1CS0026311XX-0100V0
https://sounds.bl.uk/Accents-and-dialects/Early-spoken-word-recordings/024M-1CS0026311XX-0200V0