katsurashareware forum

macOS itself doesn’t provide a way to monitor the audio output.

there are third-party solutions to “route” the audio output as an audio input.

you can use soundflower to monitor the audio output from iTunes, for example, with ProLevel.

1. set the output as “Soundflower (2ch)” in the System Preferences "Sound"
2. launch the SoundflowerBed app, and set the output as “Built-in Speaker” in the SoundlowerBed menu to hear the iTunes output, for example, from the built-in speaker. https://github.com/mLupine/SoundflowerBed/releases
3. set the input as “Soundflower (2ch)” in ProLevel

https://github.com/mattingalls/Soundflower/releases/

Dec 18, 2014: Signed Version for Yosemite/Mavericks/El Capitan/Sierra/High Sierra

https://github.com/mattingalls/Soundflo ... /tag/2.0b2

IF INSTALLING ON HIGH SIERRA
The first attempt to install will display a security alert, then fail. Afterwards, you need to go into System Preferences "Security & Privacy - General" pane and give permission to allow the install signed by the developer "MATT INGALLS". After giving permission, you will be able to run the installer successfully

https://github.com/mattingalls/Soundflo ... -2.0b2.dmg

https://github.com/mattingalls/Soundflower/releases/

"The SoundflowerBed app is retired. A new replacement is in the works. In the meantime, you can take your chances with an older version of Soundflowerbed, but you can do a lot with a Multi-Output Aggregate Device. Here's an example:

Say i want to play some audio in iTunes, but record it in Quicktime while listening to it out of the built-in speakers. Here is how i would set it up:

*in iTunes:

start playing audio

Open Audio MIDI Setup: (found in /Applications/Utilities)

hit the '+' button in the bottom left corner and select "Create Multi Output Device"
in the the panel that appears on the right, select "Built-in Output" AND "Soundflower (2ch)"
then hit the button with the gear icon bottom left and select "use this device for sound output" (you should still be hearing your iTunes output -- it is now going to both Soundflower and the built-in speakers)

Then In Quicktime:

create a new audio recording
in the popup menu next to record button select "Soundflower (2ch)" as the input
(you should now see record levels changing)
hit record!"