A present-day sound mixing desk accepts a number of audio signals from microphones and/or tape machines and can be used to alter the tonal character of the signals, change the sound level, mix signals together and route them to selected outputs. An example of the use of a mixing console is given and this general treatment is then extended to a discussion of the advantages that can be obtained by implementing the mixer functions in digital form. An experimental digital mixer is described and the advances in hardware processing techniques since the inception of the equipment briefly reviewed. Finally, an indication is given of the form of the next generation of digital mixing consoles.