OK.  I have two theories.  The first is a question:

1.  I know what libasound_module_pcm_jack.so does -- but what does libasound_module_pcm_jack.la do?  It has been said that the ALSA2Jack plugin won't work at all without the .la file, but it was working perfectly over here without it.  Is the .la something Ubuntu-specific?  Or...?

2.  Theory #2 is the better because it accounts for the fact that it was working pretty well:  might the ALSA2Jack plugin have trouble handling multiple streams at once?  If so, is there a streams-mixing plugin I can use before ALSA2Jack, to make this work better?

J.E.B.