How to double the length of a recording on Mac

I have an MP3 music recording that I want to increase in length. It’s too short for background music on a slide presentation. It’s stereo. How do I replicate the original tracks to make it twice as long as it is? Duplicate just creates two more tracks vertically. I want two more tracks appended to the original stereo recording. Horizontal not vertical.

While you have two of them, one over the other, use the Time Shift Tool (two sideways black arrows) to push the bottom one later (to the right). They’ll both play at the same time and you can tell where you are with the MUTE and SOLO buttons on the left of each track.

Then use the fade, cut, etc, etc and other editing tools to make the extended music fit without making it sound like you did anything.

When you get it exactly the way you want it, File > Export: WAV (Microsoft). That will make a new sound file with both tracks smashed together.


We would urge not to make another MP3. If you do, the new MP3 will have lower sound quality than the original. That’s the way Audacity works with MP3s.

If you make a WAV type sound file, the quality will stay the same.

If you do need to make a new MP3, you’ll need to install the “Lame” software. Audacity won’t do it by itself.

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I don’t think that I am getting this. I pushed the bottom track to the right edge of the screen. The top track went with it. That left two empty horizontal spaces where the tracks used to be. Nothing plays in this space, obviously. I don’t think that this is the result that you intended.

Isn’t there a way to select one track, Copy and paste it onto the end of track one?

Do the same with track 2. Done. That’s the way I handle extending a mono track to be longer.

Got the part about lame. I did that already on Mac and my old Windows machine.

Duplicate just creates two more tracks vertically.

Exactly. That’s the “second show” you will be pushing to the right. A stereo show is two blue waves, Left and Right top to bottom. Duplicate will give you two stereo shows.

You can select the bottom show by clicking just above MUTE. The stereo track should turn a different shade.



I was just playing around and trying a few things, and boom! got it done. I reduced the magnification so I could see the whole track and then some. Then I selected (highlighted the whole track, both at the same time, and did a copy, and paste at the cursor location, which was at the end of the stereo track.

Now another problem. But I will start a new thread since it doesn’t pertain to stacking tracks end to end.

To answer your original question, use the “Repeat” effect: