For what this "concert" cost, billed as a Rock Concert, not a Musical play, I would expect that he sing what he can sing, and not use backing tracks to help his voice. If he can't sing it anymore, then hire a SINGER to stand front and center while he plays the bass, and sings where he CAN.
I know he's in his late 60's and he loves this album (like many of us do) but let's face it, I'd rather see this billed as a night at the Theater than a rock concert.
And make no mistake, I really love this album, and I loved it when he performed at the Wall in Berlin back in 1989. This would have pissed me off had I paid my well over $100 to see it.