In 2014, Cycling '74 passed stewardship of Soundflower to Rogue Amoeba, but we ultimately didn't have the time or resources to improve the product. Initial development and maintenance of Soundflower was done by Cycling '74. Soundflower is an open source kernel extension for MacOS, designed to create a virtual audio output device that can also act as an input. After downloading, control-click on Soundflower.pkg and select 'open' (then click 'Open' in the 'unidentified developer' alert window).
Soundflower creates a virtual audio interface which has a number of inputs and outputs.