FAKE!!!!!
Twds the end you hear full stepped notes on top of what they are fingering then triads on the iPad 4th gen
Where is the disclaimer it took several iPads to play this?!?!
In Garageband you can 'layer' multiple tracks on top of each other, therefore the additional notes could have been recorded earlier and now that track is being played back in the background while the 'live' playing happens on top of it.
This is actually confirmed in the video as you can clearly see when the regular iPad is first shown that the play button is pressed in GarageBand indicating that there is a background track being played also.