The Rock Band 3 Midi Pro Adapter technically came out at the end of 2010, but they're still pretty hard to find out in the wild. Best Buy had a few at launch, but that was about it. Those musicians that wanted to try connecting their MIDI drums, keyboards and guitars up to RB3 were up a creek. That will change says Mad Catz VP of Marketing, Michael Greco. He told Destructoid yesterday that we can expect the product to be hitting store shelves "full force" any day now. They're caught up now and there shouldn't be any supply problems going forward.
I got to see the Midi Pro Adapter in action yesterday on both a Roland Lucinda keyboard controller and the Rock Band Stratocaster. On the keyboard it sat on the face, in tabletop mode. One simple cable from the MIDI output of the board did the trick and worked perfectly On the guitar, there's a clip that mounts the adapter to the guitar by way of the strap holder. It looks clean and holds well. You can see examples of both in our gallery below.