I was able to mix the audio by playing it on two separate
channels; I could convert that to a ByteArray using the
SoundMixer.computeSpectrum static method - but It looks like the
array is not exportable to be a useful audio file.
The Digimix project (which I can't seem to download
anymore??) states that it can do that - but I'm not sure how they
would have accomplished it....
Possibly there a way to integrate with the Java Sound Class
in the future.......