I was thinking that Teensyboy didn't act as a USB Host but just as a Device?
Ow, can anyone confirm this?
At least, you can add these shields to an arduino (or Teensy or RasPi) : http://www.hobbytronics.co.uk/usb-host-midi
Oh nice! That seems a lot simpler than I had imagined.
The only electronics I've messed around with are Gameboys, so I'll need to investigate a bit, but theoretically I would just need the Raspberry Pi, a midi connector, and that USB host board right? (Give or take)...