I want to play an instrumental track that a friend uploaded to YouTube and simultaneously sing into the Mac's mic. And I want to record the mix of these two sounds using Audacity.

I've tried using various solutions for similar (but not exact) situations that are described on Ask Different. I've tried various combinations of "Aggregate Device" in "Audio Midi Setup." Nothing has worked so far.

I have the following installed on my computer: Line In, WavTap, SoundFlower.


(I have a MacBook Air with a built-in mic, with OS X Yosemite.)

2 Answers 2


I'd approach the problem from the opposite end...

Get the YouTube audio track into Audacity first.

You can use iTunes to extract audio from video

  • In prefs > General, click Import Settings... & change 'Import Using' to WAV [remember to set it back to your preferred audio format afterwards]
  • Drag your video into iTunes, then go to the Movies tab
  • Select the movie, then File menu > Create New version. Hold the Alt ⌥ key & the 3rd option will ungrey, allowing you to save the audio separately.
  • Import this to Audacity.

Then you have all day to record your vocal track separately; add reverb etc & export the finished mix from Audacity.

This approach not only gives you the time to go back & edit mistakes etc in the vocal track, it also avoids the essential difficulty of trying to live-record 2 audio streams to separate tracks without professional audio equipment.

  • Good answer, I upvoted it, and will probably follow it. Thanks! For the "correct" answer, I'm going to hold out for an answer that tells me how to pre-mix the two streams, mainly so I can get a technical understanding of how that would work. Oct 11, 2015 at 16:30
  • TBH, the only other way to do it without pro hardware would be to separate the streams using Audio Hijack - but that's 50 bucks. There used to be an earlier routable audio structure called Soundflower but that's getting very flaky under anything newer than Mountain Lion - kernel panics are not uncommon.
    – Tetsujin
    Oct 11, 2015 at 16:34

Get the track cued up to the start,
click "Tracks" and select "Add New -> Mono Track".
You are now going to be making a multitrack recording!
Highlight this new mono track and select "built in Microphone" for its input source.

Now you can start the music and record the vocal on this new track. Later it will need to get mixed down to mono or stereo.

PS GarageBand was made for doing this. But Audacity can too.

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