Video · Replace Audio
Swap the soundtrack and leave the picture well alone.
Use a song, a voiceover or the sound from another video. The picture is copied without re-encoding, and the result always ends exactly when the video does.
One-time purchase · macOS 26 Tahoe or later, Apple silicon recommended
How it works
Three steps, start to finish.
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01
Open Replace Audio
Press ⌃⌥Space and type “add music”, or pick it from MightyBench’s menu bar icon.
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02
Add videos, then the new audio
Drop in your videos and choose a New audio file. Turn on Loop to fill for short tracks, and raise Original sound to keep the old audio underneath.
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03
Press Replace Audio
Each video gets its new soundtrack as 192 kbps AAC, in a new dated folder in Downloads › MightyBench. MOV stays MOV; others become MP4. Originals are untouched.
The details
Small things, done properly.
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No re-encode, no quality loss
The video stream is copied as it is, so the picture loses nothing and the job finishes quickly.
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Always ends with the video
The result is exactly as long as the video: longer audio is cut, and shorter audio loops or ends in silence.
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Keep the original underneath
Raise the Original sound slider to keep the old audio quietly under the new track, at its own volume.
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Dates and metadata kept
Recording dates and other metadata are carried over from the original video to the new one.
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Sound from a song or a video
The new soundtrack can come from any audio file or another video, and is saved as AAC at 192 kbps.
Specs
Replace Audio, at a glance.
New soundtrack, untouched picture.
| Opens | Videos: MOV, MP4, M4V, MKV, WebM, AVI, MTS. New audio: any audio file or video |
|---|---|
| Saves as | MOV stays MOV, others become MP4; picture copied, audio AAC 192 kbps |
| Settings |
|
| Needs | FFmpeg, installed in one click |
| Originals | Never changed |
| Saved to | Downloads › MightyBench › date Replace Audio |
FAQ
Questions about Replace Audio
Anything else? Email support@mightybench.com and a person will reply.
How do I add music to a video on a Mac?
Open Replace Audio, drop the video in, choose the song as New audio and press Replace Audio. Turn on Loop to fill if the song is shorter than the clip.
What if the song is longer or shorter than the video?
The result always ends with the video. Longer audio is cut; shorter audio loops when Loop to fill is on, or ends in silence when it’s off.
Can I keep the original sound under the music?
Yes. Raise the Original sound slider and the old audio plays quietly underneath the new track, at its own volume.
Will replacing the audio lower the video quality?
No. The video stream is copied without re-encoding, so the picture is unchanged and the job is fast. Only the audio is new, encoded as AAC at 192 kbps.
Can I use the sound from another video?
Yes. The new audio can be any audio file or a video, and only its sound is used.
What does Replace Audio need to run?
FFmpeg, which MightyBench installs through Homebrew in one click. If you already have a copy, you can point MightyBench to it instead.
Plus forty-eight other tools.
Replace Audio comes with every other MightyBench tool: video, audio, images, PDFs and on-device AI in one native Mac app. Pay $39 once for one Mac, with every MightyBench 1.x update included.
One-time purchase · macOS 26 Tahoe or later, Apple silicon recommended