Hallo David!

...

I've now switched from gcc 4.0 to 3.3 using gcc_select, but output
remains the same...

yes - should not matter, I compiled it with gcc4 ...

Compiling sndfiler against dev_0_39 instead of MAIN, I get:

well, you can do both - compile against devel or main - as said before, for devel use Makefile, for main use Makefile.pd_main ...

...

gcc: unrecognized option `-pthread'

sorry, I have no experience in compiling on osx ... you will have to adapt the Makefile.pd_main, because I never compiled the new version on osx ...

I don't know why gcc does not know -pthread - maybe you have to install pthread on your system ? (maybe an osx experienced developer can help us here?)

...

...

I don't -have- to do ogg, could do mp3 instead...would that be
possible?

sndfiler does not support mp3 - only ogg and all formats supported by libsndfile ...

LG Georg