On Wed, 21 Oct 2009 12:13:53 -0400, Harry Aspinwall
<[log in to unmask]> wrote:

>A few words in Ragda-Sazgwa are onset-less, but Proto-Sazgwa tone
>derives in full from codas (mostly voiced vs. [or resp.] unvoiced, but
>also for sibilance), creaky voice, or long vowels, 

Mm, good.  I've seen it argued that a voicing contrast in onsets (strictly;
this doesn't go for e.g. onset breathiness) will only precipitate tone when
tone is already contrastive.  

>4. High tone before sibilant -

That I don't expect.  Fricatives and (I think) especially sibilants tend to
lead to low or falling tones; if sibilants broke the general pattern that's
what I'd expect of them.  

>Also out of interest, does anyone else have distinction between velar
>and uvular fricatives? Natlangs? It doesn't seem unlikely, but I
>haven't stumbled across one so far.

It's not that uncommon in natlangs.  Several examples could be named; I'll
just give you Seri
which has this contrast in fricatives without having it in plosives, or
anywhere else.