Soundflower is a Mac OS X (10.2 and later) system extension that allows applications to pass audio to other applications. Soundflower is easy to use, it simply presents itself as an audio device, allowing any audio application to send and receive audio with no other support needed. Soundflower is free, open-source, and runs on Mac Intel and PPC computers.
Soundflower presents itself as one of two audio devices (2ch / 16ch). The 2-channel device is sufficient for most situations.
To send the output of one application to another, select Soundflower as the output device in the first application and Soundflower as the input device within the second application.
If an application does not allow you to specify audio devices, you can make Soundflower the default input or output device inside the Sound panel in the System Preferences, or with the Audio MIDI Setup utility application.
The 16-channel device is provided for more complex routing situations, and can be used with more than two applications simultaneously if the applications support audio routing to any channel, as Max/MSP does.
Note that Soundflower’s audio channels represent a global audio space. If more than one application is sending its output to the same channel, the audio will be mixed. If you want an application to send and receive audio through Soundflower, (for instance using Max/MSP to manipulate and return another application’s audio) you must send and receive the audio on different audio channels or a feedback loop will be created.
Soundflower 1.3.1 requires OS X 10.2.8 or later. Soundflower 1.4 requires OS X 10.4-10.5.