System: 2011 iMac, built-in microphone, Mountain Lion.

This is a two part question. First the more basic scenario, second the more-niche scenario that I hope to ultimately solve.

I want to share my Mac audio over Skype, while still being able to simultaneously talk to the person on the other end of the call. As of yet, every combination of options I have tried (dozens) involving Soundflower, aggregated devices, and even LineIn.app has completely failed.

So firstly, what are the precise steps needed to get my Mac audio (say, youtube videos playing in a browser...) to transmit over Skype along WITH my voice from the built-in Mic?

Now for the ultimate solution I hope to achieve. I want to be able to collaborate musically with other parties, using a program called Reason from Propellerhead Software. Reason has its own audio interface setting - a single setting for both input and output. I use the Propellerhead's own audio interface called "Balance" as my audio device for the software, providing my physical I/O as well as a headphone mix.

I want to be able to merge the audio output of Reason, along with my voice via the built-in mic of the Mac, and send them together over Skype so that the other person can hear what I'm doing in reasonable fidelity (subject to Skype's limitations, of course).

Can anyone provide the exact steps to share Reason's audio along with my mic, over Skype?

If 3rd party software beyond SoundFlower/LineIn is required, I'm OK with that... though this should work with just SoundFlower even. I even had it working a couple months ago but can't seem to replicate the result again.

  • Don't you think that even small audio delays will render the audio experience rather out of sync? Could be tough to get it synchronous across all involved users.
    – nohillside
    Commented Nov 10, 2013 at 9:17
  • 1
    Not a problem as this isn't about live performance collaboration. This is about discussion of the tools being used and just to get a generally decent ability to listen to the audio. But regardless of quality, this should work technically, and I can't get it to at all, even poorly.
    – JVC
    Commented Nov 10, 2013 at 18:49

2 Answers 2


FWIW, after a lot of tinkering I solved this issue using Soundflower and the excellent Ladiocast application. Never looked back.


  • install Soundflower from github, this gives you 2 new audio devices
  • install Ladiocast from the Mac AppStore
  • configure Skype to use the Soundflower (2ch) device as microphone, built-in speakers as output
  • start Ladiocast and select Soundflower (2ch) as Main Output
  • select the built-in microphone as Input 1, send to Main Output (using the buttons)
  • select Soundflower (64ch) as Input 2, send to Main Output
  • configure your Mac to send output through Soundflower (64ch) using System Preferences
  • if you want to listen to yourself, configure e.g. your headphones as Aux Output 1 and send both Inputs to it as well

Now the other party will hear your Mac's audio plus your voice over the microphone. You can test this with Spotify and the echo123 Skype test service. Ladiocast must be running for this to work; quitting Ladiocast ends the sound links.

  • Can you share some details on how you used these applications to solve the problem?
    – nohillside
    Commented Apr 15, 2020 at 20:06
  • Yes, added howto.
    – mvreijn
    Commented Apr 15, 2020 at 21:27

Turns out I had some strange Core Audio driver issue. Every time Skype was running, process "coreaudiod" would fire up and begin to hog CPU like crazy. I fixed permissions on my boot volume and it fixed a bunch of stuff related to iTunes, which apparently also fixed whatever was going on.

Once the coreaudiod issue was resolved, here's the setup that is working perfectly:

  1. Skype "microphone" (input) set to Soundflower (2ch)
  2. Aggregate Device created, consisting of Built-In Microphone and Soundflower (2 ch.)
  3. Reason set to use the Aggregate Device
  4. SoundflowerBed set to output to Balance.

Now all I have to do is create an audio track and enable monitoring, and I can hear myself in the mic, while normal Reason audio flows out both to Skype and my Balance to my headphones, and all is well with the world.

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