The world of classical music has been shaken by the Joyce Hatto scandal. For those unaware of the affair, Joyce Hatto was a pianist whose career was cut short in the 1970's due to cancer. However, in 1989 she started recording again and producing CDs with her husband's independent record label. When she died in 2006, The Guardian pronounced her "one of the greatest pianists Britain has ever produced".
Unfortunately, she was not the great one, her husband's recording capabilities were. It seems like all her output since 1989 had been copied from other artists. How was the trick discovered? Through iTunes of course! Tipped by readers, music magazine Gramophone tested several of Hatto's CDs on the database, only to discover that iTunes recognised them as being recorded from other artists. iTunes believed that the first CD was from Laszlo Simon, while the second had been the work of Yefim Bronfman. After the deception had been uncovered, William Barrington-Coupe, the guilty widower, admitted to it.
How did iTunes recognise the original? iTunes uses Gracenote's CDDB, a database which enables third party applications to identify individual CDs so that it can automatically discover cover art, artist, title and label. CDDB is powerful enough that it will identify songs without metadata if they are in the same correct order and have the same length as the original. This is because CDDB creates a unique fingerprint of each CD on the database called a 'discid'. This contains information about the CD's song order, length and other data. It seems like Mr Barrington-Coupe's error was to copy the CDs as they were instead of mixing them a bit.
As any amateur CD-ripper knows, CDDB will not identify your own compilations.