Pronunciation of Tang Dynasty Poetry It was related to me that Tang Dynasty poetry is meant to be pronounced in the style of the Cantonese dialect.  Is this correct, incorrect, or a subject of contention?
well,  this answer is "limited" only, in relation to poetry in 唐 dynasty &amp; cantonese.

1   cantonese (and several southern dialects/languages) is highly correlated to middle chinese, which was used in 唐 dynasty.

2   cantonese still has 入聲 (entering tone), while mandarin lost it. e.g.

屋 uk1　sound file

沃 yuk1　sound file

燭 juk1　sound file

in mandarin, these three are pronounced as:

屋　wū　(陰平, dark level)

沃　wò　(去, departing)

燭　zhú　(陽平, dark level)

3   韻書 (rime dictionary), e.g. 切韻, 廣韻; one can find character based on cantonese, or other southern dialects / languages, but not mandarin.

4   poetry in 唐 dynasty had rules and patterns. compare to a language without entering tone, characters not in accord with rime dictionary; cantonese is a better choice.

last, there was a book 文鏡秘府論 by japanese monk 遍照金剛　(空海), which was written at about 809. it talks about the rules /  patterns of poetry &amp; chinese phonology in details. 

the internet archive has a copy:

https://archive.org/search.php?query=文鏡秘府論

or, 文鏡秘府論匯校彙考

have a read, please.