I do software FX on my guitar using my Mac and a USB interface, but the produced output sound goes back to the interface - I can listen to it but I can't record it on my Mac, only the input sound device pre-FX.

I'm aware of "virtual cables" and "virtual sound cards" but I understand Windows for instance can allow direct capture of a sound-card output.

Is this something available on macOS and if so, which versions - and any general information I should know?


Apple's really crappy UI with useless documentation for MacOS's audio is the Audio Midi Setup. Once you find and open it, select menu Window/Show Audio Devices.

That in conjunction with some virtual audio routing software like Soundflower may get you want you need.

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macOS doesn’t have anything built in, but you can capture the audio using a tool like ffmpeg. See the following question/answer for full details on how to structure the command.

We can do the same with any audio device. You would simply reference the ID of the sound device that you’re capturing from. Using the linked answer as a reference, if your sound card device happened to have an id of “2” the command would be:

ffmpeg -f avfoundation -i ":2" -t 10 audiocapture.mp3

That command would capture 10 seconds of audio from the device and save it to a file audiocapture.mp3.

  • I'm more interested in at a low OS/driver/hardware level if/how this is achieved in MacOS. Clearly it is supported for ffmpeg to work but is is some standard API or very low-level hackery?
    – Mr. Boy
    May 12 '20 at 17:35
  • macOS being the OS and “not built in” answers the “OS” question. avfoundation is the API and macOS doesn’t give you access to drivers or the hardware directly. Windows doesn’t allow you do access the hardware or drivers directly either. You have to go through the HAL (hardware abstraction layer)
    – Allan
    May 12 '20 at 17:40
  • How do you find ID of sound card?
    – Natsfan
    May 12 '20 at 19:07
  • I think expanding on what avfoundation is would complete this answer, then @Allan. Particularly, given I have multiple audio devices, how your example selects which output it 'listens to.
    – Mr. Boy
    May 12 '20 at 19:14
  • that info is in the the linked answer. "See the following question/answer" for full details on how to structure the command."
    – Allan
    May 12 '20 at 19:24

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