You might remember Soundflower - it was a handy add-on for MacOS X that ran in the background and let you invisibly route audio between applications without needing any external wiring. It's what Inter-App Audio does on iOS, but Apple never actually implemented a similar system on the Mac, hence the need for Soundflower.
Sadly, as MacOS developed and its core systems and code changed significantly, support for Soundflower - which came out in 2004 - became patchy and eventually it stopped working on more recent versions of the OS. Happily though, there's now an alternative. Blackhole from Existential Audio is free and works in much the same way.
After installation it appears as a virtual source and destination, letting you send audio between any applications on your Mac. So you can record pretty much anything internally without ever needing to route sound out and back into your hardware. It might sound like a small thing but it can be a huge time saver. There are some reported issues around OS X Catalina but these are likely to be ironed out in time. You can grab Blackhole now using the link below.
Dec 31, 2018.
Paid software which is a little more polished and does the same thing includes Rogue Amoeba's Loopback and Audio Hijack for the Mac, or JACK Audio Connection Kit which is free and cross-platform.
Get the latest stable releases here: https://github.com/ExistentialAudio/BlackHole/releases
Learn more about OS X and audio recording: https://ask.audio/academy?nleloc=new-releases
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How To Use Soundflower
Free Inter-application Audio Routing Utility for macOS
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.
If you are hearing clicks or breakups, try increasing the buffer size of both applications (set within each application).
Applications
Since Soundflower offers a straight forward method of communicating between applications on the Mac, there are a variety of situations where you can employ it.
Podcasting
Soundflower For Windows 10 Download
Soundflower has been used extensively in podcasting by combining separate streams of audio into one source. Instead of recording an interview with Skype and only hearing one voice, Soundflower lets you publish both voices for a complete interview experience.
Cellphone
Use an application called DittyBot and Skype to access your iTunes collection from any cellphone.
Music
Record streaming audio from iTunes into Audacity, or route an audio stream from iTunes to Logic.
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Soundflowerbed
When using Soundflower to send audio to and from applications, you may find that you are not able to send audio through another device to monitor audio output. In such situations you can use Soundflowerbed, an application that resides in the Finder’s Menubar allowing you to tap into Soundflower channels and route them to an audio device.
Download: Soundflower 1.6.6 Installer (includes SoundflowerBed) -- Use this for OS 10.6 - OS 10.8
https://code.google.com/archive/p/soundflower/downloads
System Requirements
Soundflower 1.5.1 requires Mac OS 10.5.
Soundflower 1.4.3 requires Mac OS 10.4.
Soundflower 1.3.1 requires Mac OS 10.2.8 or later.
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