I have been analyzing the performances of Chopin Mazurkas and have been noticing an unusual occurence: the performances of the same two pianists always matched whenever I do an analysis for a particular mazurka. In fact, they matched as well as two different re-releases of the same original recording.
The full story about how the tracks have been slightly time-stretched, panned and EQed before being rereleased is covered in a recent story in Gramophone.
Craig has made a set of performance correlation scapes showing the similarities between a number of mazurkas. It is interesting to notice how music technology can play an important role in recognising and building evidence of such activities. This will probably be more important in the future.