bradrn wrote: ↑Sat Aug 10, 2019 6:18 am
On the contrary, I would be surprised by such a system: I would expect tones to be equally distributed across syllables. (I wonder if anyone has studied these statistics? I would be fascinated to get some concrete data on this!)
The Proto-Tai tone system shows an unequal distribution. Syllables ending in a plosive are called tone D ('checked' or 'dead' syllables), other syllables ('live' syllables), which to careless listening end in a vowel or resonant (/l/ or a nasal), are split between 3 tones, labelled A, B and C. This tone system lasted until recently enough that is reflected in Thai spelling. The commonest of A/B/C, dubbed A has no tone mark; the second commonest, dubbed B has a tone mark which is a single vertical stroke; the rarest, dubbed C, has a tone mark which started as a vertical stroke plus a horizontal stroke, but now looks surprisingly like a digit '2'. Looking at a line of text, most syllables have no mark. The numerous loans from Pali and Sanskrit have been assigned to tone classes A and D, increasing the bias towards tone A.
Historically, this may not be so surprising. One of B and C is supposed to reflect a final /s/, and the other a final glottal (possibly several different glottals).
Nowadays, A, B and C have become 5 tones. One of the tones derived from A is known as the 'common' tone, and remains the commonest, but its predominance is much less.
There's a corpus analysis for Thai (FREQUENCY OF OCCURRENCE OF PHONEMES AND SYLLABLES IN THAI: ANALYSIS OF SPOKEN AND WRITTEN CORPORA by Munthuli et al.) in
https://www.google.com/url?sa=t&rct=j&q ... 1i8EsjkCPs (too lazy to degooglise it). The modern tones derived from the old tones as follows:
mid < most A (34%)
low < some B, some D (22%)
falling < other B, some C, some D (19%)
high < other C, some D (16%)
rising < other A (9%)
The split of A, B and C is conditioned by the Proto-Tai initial; the split of D is conditions by old initial and vowel length.
There are some interesting correlations in the co-occurrences of sounds; most are to be explained by (a) the tones of live and dead syllables being two separate systems and (b) history. I've seen some elegant explanations of the non-existence of some words that even I know. There are quite a few words that could not have derived from Proto-Tai, many being recent loans from Chinese; that is why modern Thai has to add two new tone marks.