They make USB hosts that are single chip solutions. I sort of expected someone to point me to a project where someone used something like this connected to an arduino, that could read the codes from the USB, with SPI, then just relay them with Serial from the Arduino through a MIDI cable.

I might try to hack something together on my own. I think I've got a reasonable idea of what the high level components that need to be there are, and really it's just a matter of getting the host to work at all, since I'd just be echoing the commands to MIDI, and sending MIDI commands with an arduino is pretty well worn territory at this point.

I just don't really have the time, but I feel silly buying a box for more than a hundred dollars when I could probably get closer to what I want for something like $20.