Not sure exactly what you mean by "configure" ...

But, in the pulse volume volume control app I have 2 output devices: "Built-in audio ..." which I have muted and "PCM2902..." which is the USB device. I've clicked on the "set as fallback" button, but that really doesn't seem to do anything.

Now if I do "aplay -l" I get 2 cards. Card 0 is the builtin; card 2 is the USB.

If I simply do an "aplay file.wav" the file plays to the external device (I'm assuming that hitting <make default> might have something to do with this). So, figuring all is well ...

timidity mymid.mid ... it plays, but no audio.

timidity -Os  ... same as above

timidity -Od ... error "/dev/dsp: No such device. Couldn't open dsp device ('d').

It's all crazy since the timidity manual states that -Od is the default ... yet specifying doesn't work.

Just checked /etc/timidity/timidity.cfg and it appears that everything there, other than sourcing some soundfonts, is out-commented.

What is really frustrating is that I know it worked before on this computer, and I remember having a time getting it to work, and I don't recall what I did :)