Recording BlackHole with Reaper
If you're using BlackHole to route your Mac's system audio into REAPER, this guide will show you how to set everything up. By the end, you'll be able to record system audio, play it back through your speakers, and optionally record your microphone at the same time using an Aggregate Device.
Open Audio MIDI Setup.
Click the + button and select Create Aggregate Device.
Note: You can add BlackHole 2ch and your speakers to the Aggregate Device. If you'd also like to record your microphone, add it as well. Your setup should look similar to the screenshot below.
Enable Drift Correction for all devices except the Clock Source device.
To learn more about Aggregate Devices, you may click here.
Open REAPER, then go to Settings.
Navigate to Audio > Device, then set your Audio Device to the Aggregate Device you just created.
Click the + button to create a new track.
Click the track's Input selector, then choose:
Input: Stereo > Input 1 (BlackHole 2ch) / Input 2 (BlackHole 2ch)
Click the Record Arm button (red circle) on the track.
Next to the Record Arm button, click Record Monitoring and set it to Off.
Important: Disabling Record Monitoring prevents an audio feedback loop while recording.
In the Mixer, click the diagonal stripes icon to configure the Audio Hardware Output.
Under Audio Hardware Outputs, select the speakers that you added to your Aggregate Device.
This allows REAPER to play back your recordings through your speakers while continuing to record audio from BlackHole.
Click the Record button on the transport bar above the mixer, or press ⌘ + R.
REAPER will begin recording the system audio being sent to BlackHole 2ch.
Optional: If you added your microphone to the Aggregate Device, create another track and select Input: Mono, then choose your microphone as the input.