I'd agree warren. There isn't any deep burying of the chisel and then trying to lever out something that takes great force, or hard scraping of a mortise bottom or anything. The levering is subtle, like a wrist flick. It's a good technique.

I have no clue what the wood is, of course none of us probably do, but it doesn't look too hard - looks a lot like mahogany. It's interesting that he works straight through no problem and appears to have a nice through mortise.