I think what you want is to map a multisample instrument to your pads.
I'm not sure if you can MIDI map individual notes on NN19 or NNXT. In fact l think l've only ever heard people speak about this with regard to Kong.
I've hardly ever used Kong but l'm assuming its pads are MIDI mappable.
So ... load your individual notes to Kong ---> map Kong to your MIDI controller pads. Have fun with novel scales. I'd assume Kong is velocity sensitive so if you had a velocity sensitive controller, all the better (my Launchpad - the mark 1 version - isn't vel sensitive).
There's also this old piece of software, which as you can see was issued for an old version of Reason (it says Reason can't do MIDI out, but l believe it can now). It acts as a layer between Reason and your controller. Beyond that, l've no idea how it works, which is a shame really because the number 1 reason l don't buy a software is ... the manufacturer forgot to give a workflow
. Of course they may show a snazzy guy mashing up some hip hop stems crazy style on YouTube, but that means f. all to guys like me - we need example workflows as if you're explaining to a cat
(take note you Propellerheads and rack developers): http://www.deluded.co.uk/relaunch/
^^^ in fact, l think the guy in your video was using this very same program, to control Matrix, or, as per the program's description, to control some kind of custom arpeggiator?