So a question about Launchpad. Does it matter what button you hit, or is it synced to play the next proper note no matter what key you hit, and that just helps control which rows, buttons light up?

As far as I know, it does matter which button you hit, but the button layouts can be changed on-the-fly, which is what makes it look like he's hitting the same buttons but different things are happening. The layout keeps changing for different parts of the song.

But I don't know for sure, I've just looked into getting one of these things a long time ago and that's what I recall figuring out about them.

So, the orchestration is preprogrammed and he's doing the piano part?

Moving this video to blacklotus90's personal queue. It failed to receive enough votes to get sifted up to the front page within 2 days.

When you play it for real, yes, it matter.

Here he's just hitting buttons to light them up with music and not really playing. If you look carefully you can see that a lot of times he's missing and pressing in between buttons and can't keep up with music.