What's kind of wild is that most major pop stars today don't even sing at their concerts. They lipsync and put on a dance show. The superbowl has been doing this for years, too.

So if this were to happen today it wouldn't even be a big deal that their "backing track" skipped.

On the second point, I remember years ago watching the "Behind the Music" of Milli Vanilli, and that's exactly what happened. They wanted to make their own music, but the powers that be said they weren't good enough and used hired guns to do the actual recording. After the fact they tried to do their own album with their own voices, but it didn't hit. I've never heard it, so I don't know if it was due to a lack of quality or if their brand was just too damaged by the scandal.