To when, and where, did 合拗音 still have a notable presence in Japan, and are there any dialects, however minor, that still preserve the 合拗音 today?

Question

I found a book published in 1886, which contained an interesting statement pertaining to the realization of the 合拗音:

Natives of Tōkiō and the Northern and Eastern provinces omit the w after k and g in such words as Kwan-non and Hon-gwan-ji.

This seems to state that Modern Japanese speakers outside of Tokyo and the "Northern and Eastern provinces" still regularly pronounced the 合拗音 as recent as 1886. Wikipedia seems to state that the disappearance of the 合拗音 started in the Edo period. The way it's written here seems to give the impression that the "proper" way to pronounce was including the 合拗音 and that the natives of Tokyo and the Northern and Eastern provinces were the ones who were different, rather than the ones continuing to pronounce the 合拗音 (although this may just have to do with the 歴史的仮名遣い spellings which explicitly include the ゎ's). That got me wondering, when did the 合拗音 end up dying out, where specifically was it still preserved, and why was it still preserved in these areas after it died out in the rest of the country? What was the reason for the 合拗音 dying out? And are there any dialects today, however minor, that still keep the 合拗音? Thanks in advance.

Answer 1

合拗音の直音化 was complete in the early 19th century in Edo. 合拗音 was more or less preserved until the late 19th century in many western dialects, and it was preserved until the 20th century in a few western dialects. Probably there are no dialects where the distinction is still widely preserved today.

日本語における合拗音の消失

江戸語では十九世紀初めにはすでに直音化していたのに対して，上方語ではあまり直音化が進んでいなかったことを物語っている．江戸語では『音曲玉淵集』に「くわの字，かとまぎれぬやうにいふべきこと」と注記されるように，上方語よりもいち早く十八世紀初期には合拗音の直音化が生じていたことがわかる．これに対して，上方語では十九世紀に入っても遅い時期に変化したようである．

"Modern standard" Japanese as we use today is based on a dialect spoken in Tokyo (Yamanote kotoba), but historically, dialects in western Japan tend to retain more elements of older Japanese, and sometimes they have been seen as more orthodox. It's not surprising to me if a book published in 1886 treated western Japanese as being more standard.