Is the concept of syllables pronunciation-relevant in languages with mora-based pronunciation?

Question

Japanese pronunciation is mora-based (correct me if there is a better word), i.e. each mora is pronounced with equal length.

Still I sometimes see the concept of syllables used, e.g.

 疲労 /hirō/ 'fatigue', 2 syllables /hi/ and /rō/, 3 morae
 広尾 /hiroo/ (location name), 3 syllables /hi/, /ro/ and /o/, 3 morae

The justification for the 3 syllables in /hiroo/ is that there is a morpheme boundary between /hiro/ and /o/. However, in my opinion the 2 words are pronounced exactly the same.

Assuming that I am correct, what purpose does the concept of syllables serve? I can see that in other languages, it might make sense to distinguish between long vowels and double vowels (e.g. the former might be approx. 1.5 times as long as short vowels, the latter twice as long), but since Japanese is mora-based (i.e. both are twice as long), does the distinction serve any purpose?

Answer 1

In Japanese, syllables have an influence on pitch accent in some dialects, including the standard.

In particular, in the standard dialect, only the first mora of a syllable can take stress. That is, for example, /ha.ɴ/ and /haꜜɴ/ are permissible but */ha.ɴꜜ/ is forbidden.

In the Kagoshima dialect, both morae in a bi-moraic syllable will have the same pitch. Particularly, Wikipedia gives an example of how accent is affected in a related dialect: The morpheme /mono/ is often reduced to /mo.ɴ/ in colloquial Japanese, changing the number of syllables but not of morae. Since in an accented phrase the accent is localized on the penultimate syllable, this causes the accent of "獣が" to shift from [kédámònógà] to [kédàmóɴ̀gà]. (In this dialect, accent is realized as a high pitch on the first mora of the syllable, and the adjacent morae are low-pitch.)

(This doesn't apply to Kansai dialects, whose pitch accents are moraically based, nor trivially to those dialects that lack accent.) See also http://en.wikipedia.org/w/index.php?title=Japanese_pitch_accent&oldid=490727319#Syllabic_and_moraic.

Of course, this doesn't require analyzing them as syllables. One could just define "mora" = "syllable", and express the rules as "syllables cannot take stress when followed by a vowel", "adjacent vowels must have the same pitch within a morpheme/word", et cetera.

Japanese accent patterns are generally based on phrasal units, which are generally longer than a single morpheme (for example phrase-ending particles are included). Therefore I'm suspicious of the claim that there's a distinction between /VV/ (within a morpheme) and /V V/ (across morphemes) when the accent pattern of the constituent morphemes is the same.