When I look at phonologies on Wikipedia, such as Xhosa or Chinese, it typically goes through the base I would say "features" of the sound system: what are the consonants they use, what are the vowels, if there are tones, clicks, stress, that sort of stuff. It seems at some level it is about the atoms of sound, like the consonants and vowels, each of which are for all intents and purposes are one base sound. Even with aspirated consonants, it's still overall one general sound.
But then some phonologies go beyond this atomic sort of level, and add on diphthongs, or consonant clusters like
tɕ (or sometimes with the arc,
t͡ɕ). These things appear as a single unit, but I would call it a second layer of composition, the second level of building blocks on top of the base sound features (consonants/vowels/stress/tone/etc.). Another second-level I would say is long vowels. In the "Xhosa vowel phonemes" chart on Wikipedia, it lists both long and short vowels. But if I were putting together a phonology, it seems it would be more "pure" to just list the base vowels which get used, at level 1. Then long vowels go into the level 2 group, along with diphthongs and consonant clusters.
Then some might go a little further depending on the language, to syllables, or things like in English, longer consonant strings that appear in words, like
-md or things like that. I would say these are getting into level 3 of composition or something like that.
My question is, what should go into a good phonology? How should it be organized? What should it include, and what should it leave out? To narrow it down, if I just collected the base consonants (or consonant + aspiration/velarization/etc., i.e. any primitive sound whole), and left out diphthongs and consonant clusters (what I am calling level 2 stuff), would that be a useful phonology? Or must it include the diphthongs and other "higher level" things/features of the sounds produced too?
I am playing around with a conscript for writing pronunciations for a fantasy project, and have begun collecting the consonants and vowels off Wikipedia to put into "phonological charts", but I'm realizing I don't have a clear definition/sense of what that actually is in the end. Some include diphthongs, some don't. I would personally move the diphthongs and level 2 stuff into a higher level thing, maybe not called part of the phonology. But I'm not sure. What goes into a phonology in the end?
If we are going with diphthongs in the phonology, and consonant clusters, why not just go and list out every possible sound combination (of say 1 syllable) which can be used in a language? I have never seen that done, but if you take picking sound combos to the extreme, you would end up listing out every possible thing you could say in the language. Not sure why diphthongs, for example, are chosen, but not other common sound sequences. That sort of stuff.