When does pitch accent reset?


My understanding of phrase-level Japanese pitch accent is that each "unit"
initially has low pitch, followed by high pitch (LH), then a drop after the
accented syllable, if there is one. As such, apart from a "reset" of the
pitch, there can never be another LH contour after the initial LH, since an
accent can only either cause an HL contour, or maintain an existing LL
pattern.

But for larger units -- different types of phrases, or multiple phrases, what
does a "unit" correspond to? When should pitch accent be 'reset'?

Also, what happens with single-syllable accented words like 蚊? Does 蚊は have
accent LL, with the rest of the phrase in L as well?




For words which are called 'accentless' (ex: 端) which end on a high pitch,
that pitch is continued to the following word (including particles). That
pitch can be continued across several words depending on whether the words in
the middle have accents or not.

Examples:

[code]

    行った・こと・ある
    L    H ・H H ・H L
    
    そんな・気・が・する
    L    H ・H・H・ H L
    
[/code]

Here, "行った" and "気” are both accentless.

In both cases, the last word (ある and する) have HL accent pattern (to begin
with), so the accent of the phrase drops there.

Another place where accent carries over is in compound words, for example:

[code]

    あお・じゃしん　 （青写真）
    L H ・H　L  L
    
[/code]

Normally, あお is (HL) and しゃしん is (LHH), but in a compound word you can see the
accent stays high across their boundary.

[Here](http://selftaughtjapanese.com/2015/01/13/japanese-intonation-changes-
in-two-word-compounds/) is an article I wrote some time back about this with
some more details.

For your last question, according to [this
dictionary](http://accent.u-biq.org/ka.html), 蚊 is accentless so it's accent
would carry onto the next word(s) until there is a drop in accent.

