Standard Romanized Xi'an (SRX) is a writing system specifically created for translating the Xi'an script into (for Humans) more easily readable Roman alphabet.
Xi'an script & SRX
With its around 200 glyphs, learning to write in the Xi'an script (kyexiin) can be a daunting task for non-native speakers. Therefore a lot of Xi'an words were spelled in different ways when written in the Roman alphabet - e.g. Xi'an and Xi'an; Kray and the technically correct Kr.ē . Especially the importance of pitch in their language gets easily lost when writing in our human scripts.
Therefore a standardized system, the SRX, was developed to clearly mark different pitch levels. The interstitial periods (.) or apostrophs (') are similar to the Xi'an way of showing pitch in their native ortography.
Overview
Quick Guide to SRX released by CIG
Neutral pitch
naithlūn : deep understanding and appreciation for something
Both syllables of this word are in a completely neutral pitch. Neither receives more stress or emphasis. NAI (as in knife minus the 'F' sound at the end) + THLŪN (in which the ŪN is pronounced much like the 'OON' in croon.) The THL is considered to be a single sound to the Xi'an and we produce it as a contact cluster when we say WITH LOVE very rapidly. Keep your voice very neutral and relaxed when saying naithlūn and give both syllables the same mid-range, neutral pitch. Note that there are no periods or apostrophes present
Falling pitch
tyo'ma : culture
This is the most common pitch pattern in the language, especially for two-syllable words. TYO (one syllable in which you should treat TY as a consonant cluster) is at a medium high pitch and MA falls past neutral to a medium low pitch. Most humans who do not already speak a pitch-based language will hear this as the TYO being stressed. The single apostrophe signals that the pitch drops on MA.
Low pitch
m.oa : all, total, every
This pitch pattern with a single interstitial period indicates that the pitch is low. M.OA is pronounced as a single syllable, very much like the extinct terrestrial bird but with the voice kept equally low on both the O and the A, which linguists count as a diphthong. The period that indicates low pitch is typically placed after the consonant if one is present, or before the vowel if there is no consonant. A good example of this is the grammatical particle .U that marks words or phrases that provide context for verbal constructs.
High pitch
Li" : one's 'path' as life is lived
This pitch pattern with a single appended double quote (") indicates that the pitch is high. This marking occurs on single syllable words and on the second syllable when the pitch rises to high. Most rising patterns do not rise all the way to high, but in certain words it is important to "go all the way up" and when that is the case the high pitch marker is used. It's important to note that many inherently high-pitch words like Li" lose their formal high pitch when they combine in falling patters. This is the case in Li't.oua, for example. This is the SRX spelling of the Xi'an "religious" tradition that you may know commonly spelled in the UEE as Li'tova or Litòva. In this word the initial LI syllable occurs at only a mid-high pitch. Inherently high-pitched syllables are much more likely to retain high pitch when they occur as the very last syllable in a compound word. For example n.aiLi", ("minor enlightenment" from the Li'tova tradition). In this word, NAI is at a mid-low pitch or even neutral pitch and "pops up" all the way into the high range on LI. This is a rise-to-high pattern and it is fairly common in the language.
Normal rising pitch
y.a'u : this (indicating this thing)
This pitch pattern is also common in Xi'an, but somewhat less so than the falling pattern. It uses both a dot (period) and an apostrophe to show that the first syllable is lower in pitch than the second. It is important to note that this first period forms a pair with the apostrophe that follows it. They should be read together. And, the YA syllable is not necessarily technically low as you might guess. In fact, it is only mid-low. Similarly, the 2nd syllable, U, is only mid-high. Many learners of Xi'an find this ambiguity in SRX annoying and there have been Human attempts in the past to adopt a comma in lieu of a period for marking this pitch pattern because they argue it would better mimic the native Xi'an spelling diacritics. However, objections recognized, the period + apostrophe solution stands. The saving grace in this ambiguity in SRX is that in the spoken language, in almost ALL rising pattens, no meaningful difference occurs in a mid-low vs. true-low pitch departure point for the rise. That is to say, it is not really necessary to mark a theoretical true-low vs. mid-low pitch because the modern language does not make that distinction except in a few minor-world dialects that you are very unlikely to encounter and some slang. When linguists make notes on dialect using SRX, true-low in a rising configuration is marked with .. as in the Xi'an youth slang term m..âman" ("crazy like a human" — this is actually a positive connotation meaning that one is able to thoroughly enjoy oneself without any inhibition). In this term the first syllable is true-low and the rise is to true-high. You will not encounter this in everyday speech. More will follow later on other patterns, but it is also important to be able to recognize the rise-to-fall pattern as in .ithl'e'a (moral; ethics; "the right choice"). The I is mid-low. THLE is mid-high. And then the final A falls to mid-low again.
Double Vowels and Diphthongs
Next, a few cautionary words about the long vowels indicated with macrons and the double i (ā, ē, ii, ō, ū). Making a proper vowel length distinction is a bit more necessary in Xi'an than having perfect pitch. You are more likely to be misunderstood for this linguistic faux pas than for not getting your pitch high or low enough. For example, .i (choice; selection) vs. .ii (multiply; duplicate; breed). Or, al (outgoing; external; projecting externally; depart; exit; export) vs. āl (sub conscious meditation; fugue meditation; reverie). There can also be an interplay of pitch and vowel length in getting your meaning right. a (object; tangible thing) vs. a" (fit; fit into) vs. .ā (continuation; (forward) movement). ii (light; brightness; shine) could be compared to .ii and .i above. Also germane to this comparison: ia ("epic" (holy, in the sense of 'beyond belief')) vs. ii'a (plant (generic term for plant); flora (juxtaposed against fauna)). These distinctions also occur in the diphthong pairs: ai*/*āi, ao*/*āo, and oa*/*ōa. (Note that ia and ea are not technically considered diphthongs by Xi'an linguists, but many Humans hear them as such.) It is best to learn these distinctions by listening to native speakers and imitating them.
Finally, a note on u+a, e, i, o and the diphthongs: It is pronounced as 'W' in this context. Hence ua = wah, ue = weh, ui = wee, uo = woh. This remains the case when combined with other consonants. pua, nua, and kuo produce pwah, nwah, and kwoh, not poo-ah, noo-ah, or koo-oh. Similarly, 'Y' produces consonant clusters with other consonants. It is never a vowel by itself as it is in UEE Standard.
References
Quick Guide to SRX
An Overview Of The Xian Language For Diplomats