“No longer is a good or even a great performance good enough. Now we must have performances free from the “slightest glitch.” And since no one — not even a singer of Ms. Hudson’s manifest talent nor a violinist of Mr. Perlman’s virtuosity — can guarantee that a live performance will be 100% glitch-free, the solution has been to eliminate the live part. Once, synching to a recorded track was the refuge of the mediocre and inept; now it’s a practice taken up by even the best artists.”