I'm tinkering with Celimine again, and thought it might be nice to get some feedback on the broad outlines of its diachronic phonology. The consonants in Proto-C have a palatalized / velarized distinction, similar to Irish or Russian (although not every consonants in the "palatalized" is actually phonetically palatalized, and not every consonant in the velarized set is actually phonetically velarized). The inventory as currently envisioned is as follows: Palatal ~ Velar Plosives: pʲ bʲ ~ p b tʲ dʲ ~ t d c ɟ ~ k g Nasals: mʲ ~ m ɲ ~ n ŋʲ ~ ŋ Fricatives: fʲ vʲ ~ f v z ~ ʂ Approximants: ɹʲ ~ ɹ l ~ ɫ I figure at an even earlier stage, /ʂ/ developed from an unvoiced version of /ɹ/, and then got re-analyzed to pair up with its fellow sibilant /z/ instead. Or perhaps it came about as a merger of /ɹ/ and /z/, or something like that. Meanwhile, there is a vertical four-vowel system, attested in natlangs in Marshallese: /ɨ/ /ɘ/ /ɜ/ /a/ Like Marshallese, there's a bunch of allophony, but the details are different. Basically, neighboring a palatal consonant triggers fronting, and neighboring a velar consonant triggers backing, while getting sandwiched in between the two results in front-back diphthongs. So, how does that look as far as plausibility for a natural phonemic inventory? The sound changes that produce the modern Celimine phonemic inventory involve a process of displaced contrast that collapses the palatal/velar distinction in consonants and splits the vowels into an 8-vowel system with front/back harmony, and a process of intervocalic lenition that introduces a bunch of new fricatives and approximants, resulting in these modern inventories: Vowels: /i/ /u/ /ɪ/ /ʊ/ /e/ /o/ /ɛ/ /ɑ/ Stops: p b t d k g Nasals: m n ŋ Fricatives: f v θ ð s z x ɣ h Approximants: w j r l and the proto-C inventory is basically reverse-engineered to produce the originally a-priori vowel harmony and this phonemic consonant inventory, along with vowel-conditioned consonant allophony like /s/ -> [s],[ʂ], /g/ -> [g], [ɟ], with a reasonable, realistic set of sound changes. -l.