Piano player here : I am so used to only playing the 3rds and 7ths with my left hand when playing with others that when playing bass I keep leaving out the roots to give the bass player freedom , and then realising I am the bass player .
I was a trifle confused by this first video until I researched and found the second :
Charlie Hunter plays a seven-string with separate pickups for the lower three and higher four strings .
He used to busk on guitar and upright bass .
The ongoing thread about the sounds of different keys triggered a desire to hear this again :
George Shearing's interpretation of " Mack The Knife " in the relative minor .