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A PC with a high-speed burner can clone a CD in a few minutes, and for only a few pence. So Sony of Tokyo is patenting a system that exploits the higher speeds used by computer CD drives to prevent copying (WO 03/063154). The music CD is pressed with its central hole slightly off-centre, while the label side of the disc includes asymmetric markings printed in heavy paint. This shifts the CD’s centre of gravity – not enough to matter when the disc is played at normal speed in a stereo, but a high-speed PC drive finds it “impossible to maintain stable rotation”, says Sony. The disc drive then wobbles about like an unbalanced washing machine and the PC cannot make a faithful copy.