In 1773 Johann Christian Bach filed a bill of complaint in Chancery for breach of musical copyright, initiating what was to become a landmark case in British copyright law. Bach claimed that the publishing firm of Longman, Lukey & Co. had brought out unauthorized editions of two of his compositions: a ‘new lesson for the Harpsichord or Piano Forte’ and a ‘new Sonata’ for keyboard and viola da gamba.