I'm not sure why you think I don't know what other dialects sound like. I know what various languages and dialects in China sound like, and am most familiar with Cantonese, Sichuanese, Hunanese, Hakka, Shanghainese, and Yi. Yi sounds positively African and is not a fair comparison, given that it doesn't even share the same writing system and is probably an actually completely different language family. Sichuanese sounds fairly close to standard Mandarin in many respects, and I'm not confident that it's more different from standard Mandarin pronunciation than the northern speech is. My opinion stands after extensive travel throughout northern, southern, eastern, and western China.

Is this the Yi you speak of?

https://en.wikipedia.org/wiki/E_language

It appears to be a Tai Chinese creole or mixed language (like a creole but without the massive simplification in grammar).

Yi(Loloish) is definitely a different language family though that wouldn’t stop people writing in Mandarin if they really wanted to. Vietnamese, Korean and Japanese were all written as if they were Classical Chinese to greater or lesser extents until relatively recently.

https://en.wikipedia.org/wiki/Loloish_languages

I’ve heard Sichuanese described as Mandarin without tones. All of Sìchuān speaks different forms of Mandarin for the same reason Manchurians do, recent massive resettlement, though not as recent as in 东北.

https://en.wikipedia.org/wiki/Sichuanese_dialects

No, it's the language of the Nuosu people to which I'm referring. Yeah, them being a different language family wouldn't stop them from writing in Mandarin. I know that, having learned Japanese and Korean. My point is that if the original written language is different between two languages, it is a strong indicator that they come from different language families. This does not stop them from starting to use the same writing system at some point in history, especially if one of the languages has no original written form.

If Sichuanese sounds similar to Mandarin due to migration, it would certainly explain a lot. Thanks for that bit of information. But I would say that the differences between Sichuanese and standard Mandarin would be more from pronunciation differences than tonal differences.

It looks like Nuosu and Loloish are different ways of referring to the same language (group) with Lolo being the Chinese name and Nuosu being their name for themselves.

https://en.wikipedia.org/wiki/Nuosu_language

> Nuosu is one of several often mutually unintelligible varieties known as Yi, Lolo, Moso, or Noso; the six Yi languages recognized by the Chinese government hold only 25% to 50% of their vocabulary in common. They share a common traditional writing system, though this is used for shamanism rather than daily accounting.

I bow to your superior expertise when it comes to the differences between Sichuanese and Mandarin but all of Sìchuān is definitely part of the Mandarin speaking area.

The book to buy if you’re interested in this is the Language Atlas of China.

https://en.wikipedia.org/wiki/Language_Atlas_of_China