It can be very difficult to distinguish between two performances of the same piece--depending a lot on the piece, of course. Some pieces leave a lot of room for interpretation, and others don't. For the pieces that don't, about the only way to distinguish one artist from another is to listen for mistakes.

The identification of the piece in question hinged on the fact that there was an out-of-tune key in the older recording that was there in Ms. Hatto's recording, as well.