I did go and watch/listen again.
My thoughts haven't changed.
The sound actually reminded me of the power of BIAB so I found a midi file of the song and tried two BIAB styles. I didn't export and mix in a DAW didn't add the dynamics of the stripped down section or the BIG string parts but BIAB very easily covered the general feel and sounds. I didn't do anything to the MIDI melody track apart from chose an "instrument"...it's a very stilted reading of the melody which, clearly, is the opposite of the chap playing in the original post.
When using the style picker I found jazz didn't quite get me there - I had to add lounge.
I know from my 5 minutes sweep through the MIDI world that it's filled with soft/smooth/lounge/cabaret/dinner interpretations of classic songs which means the chap would certainly gain an audience amongst midi musicians if heard widely enough.

Attached Files (Click to download or enlarge) (Only available when you are logged in)
IMAGINEavoidsynthloungefunk.mp3 (7.57 MB, 4 downloads)
Loungejazzfunk
IMAGINE Eb Chicago Light.mp3 (7.57 MB, 9 downloads)
Eb Chicago light

Cheers
rayc
"What's so funny about peace, love & understanding?" - N.Lowe