user25024: I installed Soundflower with brew cask install soundflower and I see it listed:
$ ffmpeg -f avfoundation -list_devices true -i ""
[AVFoundation input device @ 0x7f9a32515e80] AVFoundation video devices:
[AVFoundation input device @ 0x7f9a32515e80] [0] FaceTime HD Camera
[AVFoundation input device @ 0x7f9a32515e80] [1] Capture screen 0
[AVFoundation input device @ 0x7f9a32515e80] AVFoundation audio devices:
[AVFoundation input device @ 0x7f9a32515e80] [0] Soundflower (2ch)
[AVFoundation input device @ 0x7f9a32515e80] [1] Built-in Microphone
[AVFoundation input device @ 0x7f9a32515e80] [2] Soundflower (64ch)

I found several threads on recording the screen without system sound (one, two, three) and one about recording audio on Linux with ALSA. I could not find how to record audio only, without video.
I also tried this command to record the audio along with the screen ffmpeg -f avfoundation -i "1:0" ~/Downloads/Screen.mov, and I got an error Conversion failed!.
How can I record system sound to a file with FFMPEG?

user1760: With 1:0 you're including the video input from FaceTime HD Camera. Try:
ffmpeg -f avfoundation -i ":0" output.wav

This only selects audio device 0 which is Soundflower (2ch).
See avfoundation input device documentation for more info.

25024: <p>I installed <a href="https://github.com/mattingalls/Soundflower" rel="nofollow noreferrer">Soundflower</a> with <code>brew cask install soundflower</code> and I see it listed:</p>

<pre><code>$ ffmpeg -f avfoundation -list_devices true -i ""
[AVFoundation input device @ 0x7f9a32515e80] AVFoundation video devices:
[AVFoundation input device @ 0x7f9a32515e80] [0] FaceTime HD Camera
[AVFoundation input device @ 0x7f9a32515e80] [1] Capture screen 0
[AVFoundation input device @ 0x7f9a32515e80] AVFoundation audio devices:
[AVFoundation input device @ 0x7f9a32515e80] [0] Soundflower (2ch)
[AVFoundation input device @ 0x7f9a32515e80] [1] Built-in Microphone
[AVFoundation input device @ 0x7f9a32515e80] [2] Soundflower (64ch)
</code></pre>

<p>I found several threads on recording the screen without system sound (<a href="https://stackoverflow.com/questions/35590500/ffmpeg-record-output-audio-for-mac">one</a>, <a href="https://stackoverflow.com/questions/19828236/how-to-record-audio-with-ffmpeg-on-linux">two</a>, <a href="https://superuser.com/questions/1154806/how-can-i-record-audio-from-the-microphone-with-ffmpeg">three</a>) and one about <a href="https://askubuntu.com/questions/682144/capturing-only-desktop-audio-with-ffmpeg">recording audio on Linux with ALSA</a>. I could not find how to record audio only, without video.</p>

<p>I also tried this command to record the audio along with the screen <code>ffmpeg -f avfoundation -i "1:0" ~/Downloads/Screen.mov</code>, and I got an error <code>Conversion failed!</code>.</p>

<p>How can I record system sound to a file with FFMPEG?</p>
 1760: <p>With <code>1:0</code> you're including the video input from <em>FaceTime HD Camera</em>. Try:</p>

<pre><code>ffmpeg -f avfoundation -i ":0" output.wav
</code></pre>

<p>This only selects audio device <code>0</code> which is <em>Soundflower (2ch)</em>.</p>

<p>See <a href="https://ffmpeg.org/ffmpeg-devices.html#avfoundation" rel="nofollow noreferrer">avfoundation input device documentation</a> for more info.</p>
