For the purpose of recording video tutorials, I want to take the output of my DAW (Ableton), and mix the audio signal with the mic input from my Sound Card. This seems fairly straight forward. Here's how I would expect it to work. My audio card is a Saffire USB 6. I also have Sound Flower installed for this purpose. Open Ableton Live Turn audio inputs off Switch audio output to Sound Flower (2 ch) Plug mic in to audio interface and ensure signal is coming in Go to MacOS "Audio Midi Setup" Click the "+", "Add Aggregate Device" (which should mix two audio streams together) Check the two audio interfaces (SoundFlower + Saffire USB 6) -(sampling rate 48,000 - clock = Saffire USB 6) Right click on "Aggregate Device", and click "Use this device for sound output" (This is the same as going in to "Sound" under system settings and changing the output to "Aggregate Device") The above should theoretically route the mic input to "Aggregate Device", and the DAW input from Sound Flower to the "Aggregate Device", and then I should be able to record the two signals in my screen capture software "ScreenFlow". However, I'm not getting output at all. Basically, I can't make sense of the MacOS Core Audio routing system. If I mix two signals by creating an "Aggregate Device", how do I tell MacOS that I want to output that signal to the Saffire USB 6? There is no way to do that. I'm very confused.