[At the end of the day karaoke is just an improved form of entertainment over the days when you would go to a bar & there would be the obligatory busker on the old piano (play it again Sam) be he a semi-pro or pro, in most instances the only difference is one also has a regular job & plays out & the other plays out .
The busker of old would have to be prepared for the punter drunk or otherwise to request to sing a song with an approach like punter"can you play so & so"pianist "what key do you sing it in" punter "pass" pianist " ok you hum it & I'll play it "
At the end of the performance the busker would congratulate the punter "well done"no matter how bad it was performed. So off goes the punter really pleased with himself with something like move over Sinatra I am on my way. Goes back to the bar buy's another 5 drinks & tells the world the guy on the piano is really great he can play anything.
Now is it really any different today except technology has given us a lot of assistance with the advent of the arr keyboard with auto rhythm & built in harmonies,key change facility,sequencing etc, it goes on. pre recorded backings for karaoke !!! It's all part of the game
So don't let ourselves get carried away.
Johnnie