Despite the large number of studies on music copyright, few works directly and thoroughly explore the role of the law in regulating music memory. By considering sound recording as a memory technology, it is a question of understanding how copyright laws attempt to manage the impact of such technology on the legal concepts of music memory and auctorial subjectivity. The article analyses the case law on “cryptomnesia” or unconscious plagiarism in the United States and Canada, i.e. cases where the defence consists of demonstrating the impossibility of access to the original work and thus the impossibility of copying it. These contested similarities reveal the dispersion of memory and creativity in a heterogeneous network comprising not only composers, musicians and producers, but also institutions and machines: the auctorial subject of legal discourse and practice is radically decentralised. The late 20th century trials on unconscious plagiarism anticipate recent legal campaigns against mash-up remix, peer-to-peer file sharing and other popular online music reproduction practices. They announce current concerns about the subjectivity of creators or consumers when intertwined with digital technologies. Copyright is the place for monitoring and standardising certain ways of listening to and storing sound recordings, in order to defuse the tensions inherent in the field of capitalist music reproduction.