Hi Fred,
I haven't been following the thread in detail, but I noticed you indicated that you couldn't get Audacity to record.
I use Audacity often to do that, but it has to be recording the right source, and I found that if I need to use it to record Composer playing then that has to be the stereo mix:
This (I think) is recording everything that goes through your card, so you need to be careful about having other programs running at the same time which will put a 'beep' through your sound card (eg like Outlook Express when some mail arrives). A downside of doing it this way is that Audacity will record the 'electrical noise' in your system as well.
By the way, I have often done what you are asking here, trying to combine the output from two sources (in my case it was Roland VSC-3, and Virtual singer (a simulated voice)). I used a useful program from Goldwave called 'Multiquence' to combine wave files (and you can shift them in time to line up the wave files) - see
http://www.goldwave.com/ . There maybe better and cheaper programs, but mine is one of the early versions and it was cheap then.
Cheers ... Clyde