How to Dub Videos in iMovie


Dubbing is the process of extracting the audio from a video clip, getting rid of that audio, and subbing in your own. It works in a variety of ways. Some could just use dubbing to swap out background music or sounds for new audio. Many viral videos on YouTube use dubbing to overlay a new voice track over existing videos like commercials. Some music artists use dubbing in a different way to replace certain parts of a live performance with better or closer to pitch-perfect versions.

Dubbing is fairly easy especially in iMovie for macOS, but could get complicated depending on how precise of a job you need done. Here is how to dub in iMovie either way.

Remove and Replace Audio in iMovie

To first get rid of the audio in a clip, you need to create a project and drag in your video clip that already includes audio. In iMovie on your Mac, create a new project by clicking the + icon at the top right. Then from your project library, find the folder containing the video you want to use or search through your Photos library. Identify the video clip, then drag it into the iMovie timeline.

Your typical iMovie storyline with detached audio.

Now select that clip, then head up to the menu bar and choose Modify. Click Detach Audio from this menu. (Alternatively, you could just control-click the clip and select it from there as I did in the screenshot.) You should notice that iMovie separated the audio and video into two files, so you’re free to edit and manipulate them individually.

From there it’s just a matter of deleting the detached audio that was originally part of the video clip and dragging in your own. Click the audio in iMovie and press the Delete key on your keyboard. Either use iMovie’s audio library to drag in a new audio file or import your own file from Finder.

Control-click the video to detach audio.

Drag and drop the new audio underneath the video clip and make sure to align it properly to prevent any silent gaps. Play it back in iMovie and you should have a video now with different audio accompaniment.

Align New Audio with Previous Audio in iMovie

This dubbing tactic applies to different needs. Aligning new audio with the previous audio is more than just dragging and dropping a new file in. Keeping alignment can disguise new audio beautifully to keep flow and continuity.

Let’s say, for example, you record yourself singing a song. Everything sounds good, but just one part is pitchy. So you record a second version and the part that was pitchy in the first recording sounds perfect now. With dubbing, you can insert solely the good part from the second recording exactly in place over the first recording so it sounds like one continuous, solid recording. You’ve effectively corrected your errors.

This requires such proper alignment so that the audio smoothly transitions between new and old clips, and so the audio matches up with the video, like your own mouth movements.

As in the previous section, first drag in your video clip and then control-click it in the timeline to detach audio.

Notice two audio tracks simultaneously for the one video.

Instead of deleting it though, this time you’re going to keep that audio. Now find either another video clip with audio or just a standalone audio clip that you wanted to use for dubbing. It’s presumably going to have much of the same content just with slight variations. If you’re dragging in a full video clip to the timeline, detach the audio from that and then delete the video clip. If it’s just audio, all you need to do is drag it in.

Drag the new audio underneath the old audio. Pay attention to the wavelength similarities so you know exactly where to place the new audio clip. The two should look like they could near perfectly overlap each other with only minimal variations.

The second audio track has different pitch than the first, so that’s what I’ll be subbing in.

Figure out where you want the old clip to stop playing and the new clip to begin, then split both clips at the same point. Do this by holding down Shift and clicking both audio clips, then hovering with your mouse over the split point. Click Modify in the menu bar and click Split Clip. (Or press Command B.)

Figure out where you want the dub to end and repeat this process at the end point. You may need to play back the audio several times to figure this out. Pick an area to split on the track where it’s easier to blend like with minimal sound. So now you should have both full audio files each with two different splits in them.

Move the dubbed part into the top row, replacing the old audio.

Delete the middle portion in the top file, then drag the middle audio portion from the bottom file in between the gap to replace it. Align perfectly for the best results.

Delete any excess audio.

You may need to resize and readjust the audio clips to get it to sound just right, so play around. Once you have your desired effect, you can delete any of the excess audio from the second audio file.

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