[LAD] mixing music and sound effects using libao

I've been playing around with libsndfile, libvorbisfile, libmodplug, and
libao to provide background music and sound effects for a game engine. I
have a solid handle on making one noise at a time, but I don't understand
mixing. At first I thought I would have to write my own mixer and handle
the channels, sample rate, and sample size issues myself. I really don't
want to have to do that. Then I noticed in the libao documentation that
nothing says that I cannot spawn two threads, each of which calls
ao_open_live() and ao_play() on different sound files. Indeed, the docs
for ao_initialize() seem to suggest this can be done with the statement
that it be called in the main thread.

I tried this and it works so erratically that I'm not sure libao was
written with this in mind. I get these results in order of likelihood:

1) "Segmentation fault"

2) "*** glibc detected *** ./threadtest7: malloc(): memory corruption
     (fast): 0x0000000001bc5390 *** Bus error"

3) "*** glibc detected *** ./threadtest7: double free or corruption (out):
     0x00000000018ba2e0 ***"

4) A bit of the first file, then the second file.

5) Only the second file.

6) Both files messily mixed with a zipping noise. (very rare)

Is libao in fact intentionally capable of doing this? If not, what are my
options for mixing music and sound effects? I really don't want to use
SDL_mixer for a variety of reasons, chiefly because my program is
terminal-only. Virtual beer if you can guess what the program is.

-- 
David Griffith
dave@email-addr-hidden
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