Really nice, beautiful music!
But… How do we know this is improvisation??
There are notes there and everything…
Guess we’ll just have to take his word for it 
It depends on how you play and if you know with basslines go with which chords.
I know anyone with reasonable sized hands can do very inspirational improvisations by keying on the black keys of the keyboard.
That’s why i consider a keyboard the most practical instrument to learn making music on very quickly.