Aha, the UI was in Portuguese. I thought the language depended on your login and was not hard-coded into the blog, guess not!
Regarding not being able to leave a comment there, can you provide more info? I checked through all the settings and everything seems fine. You just need a Google or OpenID login.
The keyboard (YAMAHA PSR E-333) has a generic USB MIDI connection (no wave audio, just midi), it works perfectly with the usbmidi kernel module and is shown as a bidirectional MIDI device in ALSA. I can record MIDI events from the keyboard using (for example) Rosegarden and also use the keyboard as a general midi output (instead of timidity++). For someone who just started messing with this, I find it pretty cool.
By the way, since ALSA is also used in Linux/ARM, I expect that it will work the same way.
I was wondering if I could actually use my phone (since it has a MHL connection) instead of a beagleboard/cubepc/raspi. The thing is I need both the HDMI and USB ports but they are both in the same connector : \