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Audio Sync in Final Cut Pro X

FCP X provides some incredibly powerful and easy to use audio sync options. In the scenarios that I am going to show you in this article we will focus on audio created using Dual System Recording. This is where the audio track is recorded onto a separate device during filming in order to be of a higher quality, while at the same time being recorded by the camera along with the footage at a lower quality to be utilized as a guide track in post.

These techniques can also be used to re-attach edited audio that might have been exported and cleaned up in Pro Tools or similar and then re-imported and requires to be re-attached to the video.  

To begin with let's have a look at manually synchronizing audio. For this you will need the original clip and a separate audio version of the same clip (presumably better quality). 

Step 1 - Create a Primary Storyline

Append edit the original footage with its original soundtrack to the timeline by selecting it in the Event Browser and pressing E. Press Cursor Up to return the playhead to the head of the clip.

Now select the audio clip of the modified sound in the Event Browser and connect it to the start of the first clip in the storyline by pressing Q.

2 Clips

2 Clips

Step 2 - View the Waveforms

Click on the Timeline Options button at the foot of the timeline and select Waveform Only. This will make it easier to see where both timelines match.

Timeline options etc

Timeline options etc

It will also help to increase the height of the clips in the same menu, and also zoom it using Command-+ until the clips fill the timeline.

Step 3 - Move into Sync

Drag the green audio clip back and forth using the Select tool until the waveforms match quite closely.

Visual sync

Visual sync

Zoom in some more in the clips to see even more detail, if the waveforms position requires more refinement select the clip and press < and > to nudge the audio clip one frame back or forth. 

Tip: Holding down Option as you press < > will move the audio clip 1/80th of a second providing a very finite refine option, for the perfectionist in you. 

Step 4 - Use eyes and ears

As well as looking at the waveform to see it sync it's a good idea to actively listen to the clip as well. Playing both tracks makes that very hard. To play back just the sound from the audio-only clip select the video clip and press Solo or press Option-S. Play the selection over and over until the clips are in sync by pressing /.



That makes it easier to see and hear when the footage is synchronized again. Once you are done tidying things up select both clips and make them into a compound clip by pressing Option-G

TIP: You can nudge the footage during playback! Try it, it’s very cool!

Now let's allow FCP X to do the work for us by auto synchronizing the same two clips again.

Step 5 - Select both Clips

In the Event Browser select the original video clip, then press Command and also select the Audio only version of the clip. 

Both clips

Both clips selected

Step 6 - Auto Sync

With both clips selected choose Clip > Synchronize Clips or press Option - Command - G.

New clip

New clip is created

A new clip is created from the original 2.

Step 7 - Select a Source

When you play the clip the sound your can hear is from the video and audio clip. To switch the clip's audio source to the better sounding audio-only clip open the Inspector or press Command-5


The Inspector

Press the Audio tab in the inspector and in the options titled Channel Configuration check the green audio track and uncheck the Blue one. Play the clip back and see how that works. 

Obviously the auto option is a very attractive one as it's so easy to use but the purist in me thinks it's important to understand both.  


David Smith

David Smith | Articles by this author

David Smith is Scotland's most qualified Apple and Adobe certified trainer. Having completed his education at Edinburgh College of Art's BAFTA winning Film School, David moved straight into TV production, first as a Vision Mixer then quickly becoming, at the age of just 24, a director of live TV studio productions. In 2001 he moved into Higher Education where he became a lecturer in TV Production, specializing in post-production and live studio production. During this time, and working with the support of the BBC, Channel 4 and independent production companies, David was instrumental in the design, development and implementation of industry-approved vocational courses across Scotland's Colleges. In 2006, after working closely with Apple Computers to create a unique multimedia studio for education at the Music and Media Centre in Perth, David became Scotland's first Apple-Certified Trainer for Pro Apps. This led on to David forming the first Apple Authorized Training Centre for Education, north of Manchester. In 2008 David made the move to full time training and joined the ranks at Academy Class, Ltd. where he continues to train industry professionals as a certified trainer across the Adobe Creative Suite and Apple Pro Apps range.


Aug 23, 2012
This is very, very helpful. But, I would like to know how you would auto synch a 6 camera multi clip with a separate audio clip. The multiclip was created in Pluraleyes. Using the waveform got me spot on, although the waveforms in the audio portion of the multi clip did not match very well with the audio clip Ibrought it. One could just recognize a "a hilltop". This was due to echo in a church and positioning of microphones.
Aug 27, 2012
David Smith
Hi Greytail,

Did you sync the audio to the video before you created the multicam clip? If not try that. Select the Audio and Video in the Event Browser, choose Clip > Synchronise Clips. Then use the inspector to select which audio clip you prefer under the Audio Tab.
Then try the Multicam clip again.
Aug 31, 2012
Hi and Thanks. I found your tutorial very clear and useful. I especially appreciate the keyboard shortcuts.

I have a question about clips synchronized manually and made into compound clips.

Can they exist outside of the project window?
I have a clip that could not be synced accurately using the synchronize command. Syncing it manually created a compound clip in the project but not in the event browser.
I would like to be able to have the sync'd clip in the browser in order to have the option of removing it from the project and then bring it back later. Is there a way to do that in Final Cut X?

Sep 03, 2012
David Smith
Compound Clips are only available in the Project Timeline at the moment.
What you could do is mark all the clips in the compound with a role, perhaps named "Sync'd" or something. Then use COMMAND-E and choose Roles as Multitrack Quicktime. Select just the "Sync'd" roles and export the clip(s). Then re-import them.
Long winded, but will work.
Oct 21, 2013
Luma Producoes
Working with clips too big when I sync the audio of a wedding he creates a giant folder occupies on my 611gb hd. Is to do without this huge file?
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