The future?

As for the wall of sound approach by The Dead, its highly impractical to use the crude noise canceling techniques they did back in the day.
Er, you mean feedback cancelling? You cant have a PA speaker with a single mic pointed directly at it... I have to admire the 'nads it took to pull that Wall concept off, even if possible someone happened to be on acid when they thought of it. "We'll stack the PA behind the band" ... "What about the vocal mics; how's that going to work?" ... "I have an Idea!"

With all the digital gobbeltygook available today, would it still be possible to pull off? Vocal mics pointed directly at the main PA speakers; only the vocalist comes through, any sound from the PA speaker doesnt. I'd put my money down on "Not".
 
Virtual DJ can separate vocals, drums and bass from memory; quality depends on the power of the computer it is running on

Apple Music can remove or reduce vocals on an iPhone by displaying lyrics and tapping the microphone button. No idea if this is done on the phone or on the server, but the quality is better than most if not all the karaoke tracks I have heard

Brian