The paper contains a brief overview of modern methods for embedding additional data in audio signals for the purposes of access control or forensic tracking. The paper also contains a summary of work carried out at the BBC Research Department in the late 1960s and early 1970s on the same topics. It also concludes that the earlier work anticipated almost all modern audio watermarking methods. In some cases, even the exact numerical values of the system parameters proposed are essentially the same as those used today in some systems. At that time, the limitations of technology and the absence of today's more serious motivation meant that the work was not continued at that time. The work also anticipated elements of today's audio bit rate reduction coding systems though, again, the future need was not anticipated at the time.