This past Shabbos, I attended a bar mitzvah where the boy’s 91-year old great-grandfather spoke. I nudged my sons to pay attention because the speaker, when quoting Hebrew, used an impeccable Lithuanian accent that is nearly extinct. Lithuanians pronounce the cholam vowel like “ay” (rather than “oh” or “oy”). It’s been years since I’ve heard phrases like “The Ribaynay shel Aylam” and “Tayreh”. Below is a synopsis and excerpt of R. Binyomin Shlomo Hamburger’s discussion of the subject. He is a partisan German-Jew but one of the few who openly discuss the variants within Ashkenazic tradition.

R. Binyomin Shlomo Hamburger, Shorshei Minhag Ashkenaz, pp. 21, 25, 27:

Four pronunciations of the cholam prevailed among Ashkenazi Jews in recent generations up to the time of the Holocaust: two in Eastern Europe and two in Western Europe. The table below illustrates these four pronunciations in both English and German as well as in the Ashkenazi pronunciation of Lashon HaKodesh.

Region of Diaspora	Accent in Ashkenazi pronunciations	Accent in German diacritic	Accent in English
Poland, Austria-Hungary	komatz chirik – אָאִי	Oi	[t]oy
Lithuania, Russia	segol chirik – אֶאִי	Aei	[p]ay
Northern Germany, Holland	patach shuruk – אַאוּ	Au	[h]ow
Southern Germany, Switzerland, France, Latvia, England, North America	komatz shuruk – אָאוּ	Ou	[g]o

…In Anglo-Saxon countries, the long “O” sound became the widespread pronunciation supported by the surrounding English language. After the Holocaust, however, many children and grandchildren of German Jews were subject to unwarranted ridicule for their pronunciation, and thus adopted one of the other pronunciations…

Those bnei Torah who were educated in today’s yeshivot do not conform to the Lithuanian cholam but to the Polish one. This comes to show that their choice of pronunciation is due not to an understanding of the subject, but merely the wish to follow their peers. They all chose the same yeshivish style which has become widespread only in this generation.