How to Add Music to a Video — Replace the Sound or Mix It Under Speech
Add music to a video without re-encoding the picture. Replace the sound or mix under speech, loop or fade the track, and set levels that work.
Updated October 14, 20268 min read
To add music to a video, open the video and the song in a replace-audio tool. Choose Replace if the clip's own sound is useless, or Mix if it has speech you want to keep. Loop the song if it is shorter than the clip, add a fade-out of a second or two, and export. The video's picture can be copied into the new file untouched, so the only part that changes is the soundtrack. The rest of this guide covers the decisions that change the result: replace or mix, what to do when the lengths differ, and how loud the music should be.
Replace or mix: the first decision
Most free tools offer only one option, which is to throw the original sound away and put the song in its place. That is the right call for some clips and badly wrong for others, so it is worth deciding on purpose.
| Your clip | Choose | Why |
|---|---|---|
| Wind noise, traffic, a crowd you do not need | Replace | The original adds nothing, so the song becomes the only audio |
| Someone talking to the camera | Mix | Speech stays, music sits underneath it |
| A product demo or tutorial with narration | Mix, music low | Narration carries the information; music only sets the pace |
| A voiceover recorded separately | Replace | The new file is the whole soundtrack |
| A dubbed version in another language | Replace | The original speech would compete with the dub |
In the replace-audio tool, the choice is one control labelled Original audio: *Replace it* or *Mix under*. In mix mode the original and the new track each get their own level, from silent to 200%, so you can lift a quiet interview while you lower a loud song. If the clip has no audio track at all, Mix is shown as unavailable, because there is nothing to mix with.
Step by step
Add the video
Drop an MP4, MOV, WebM or MKV file into the replace-audio tool. It is read on your device; nothing is uploaded.
Add the song
MP3, WAV, M4A, AAC, OGG and FLAC are all accepted. If you only want the chorus, set the Audio starts at and Audio ends at controls rather than cutting the file in another app first.
Pick Replace or Mix
The presets — Soundtrack, Background music and Voiceover — set sensible starting levels. Every control stays adjustable after you pick one.
Decide what happens when the lengths differ
Loop to fill, Play once, or Cut video to audio. The next section explains which to choose.
Listen against the picture
Press play in the preview. You hear the actual mix with the video, so you can fix the balance before you export rather than after.
Export and download
The picture is copied across as it is, and only the new soundtrack is encoded.
When the song and the video are different lengths
They almost always are. A three-minute song under a 40-second clip, or a 30-second loop under a five-minute walkthrough. There are three sensible outcomes, and each one produces a different file:
- Loop to fill. The music repeats until the video ends. Right for a short music bed under a long clip. The output is as long as the video.
- Play once. The music plays through and the rest of the video is silent. Right for a voiceover that ends before the picture does. The output is as long as the video.
- Cut video to audio. The video stops where the music stops. Right when the song defines the edit — a montage cut to a track. The output is as long as the song.
How loud should the music be?
The most common fault in home-made videos is music that drowns the speaker. Viewers will forgive slightly quiet music; they will not sit through a clip where they cannot hear what is being said. Some starting points that work in practice:
| Situation | Music level to start from | Original level |
|---|---|---|
| Music under someone talking | 25–40% | 100% |
| Music under a quiet interview | 20–30% | 120–150% |
| Music with no speech at all | 100% (Replace mode) | — |
| Ambient sound you want to keep faintly | 100% | 15–25% |
Then listen on the speaker your audience will use. A mix that sounds balanced on studio headphones often sounds music-heavy on a phone speaker, which reproduces speech frequencies well and bass poorly. If the tool warns that the mix is above full scale and will clip, lower one of the two levels; clipping is a harsh crackle that no later step can remove.
If the music file itself is much quieter or louder than your other material, fix it before you add it: the volume booster applies an exact gain without clipping, and normalizing audio loudness explains how to make several tracks match.
Replace or mix, loop and fade, then hear the result before you export. It all runs on your device, not our servers.
Add music to a videoGetting the sync right
Background music needs no syncing: it simply starts with the video. Sync matters in two cases. The first is a song whose first beat should land on a particular cut — a jump, a reveal, the moment the product appears. The second is a voiceover or dub that must match lip movements.
For both, use the Offset control. A positive offset delays the new audio against the picture; a negative one starts it earlier. Its range is worked out from the two files you loaded, so you cannot push the track entirely past the end of the clip. On the free plan the offset reaches 30 seconds either way. For a dub, do the rough timing in an editor first and use the offset for the last few frames, listening in the preview each time.
Why the video quality does not change
A video file holds separate tracks: one for the picture and one or more for the sound. Swapping the sound does not require touching the picture at all. The replace-audio tool copies the encoded video frames into the new file exactly as they were, so the exported picture is identical to your source — no softening, no new compression artefacts, and it finishes in seconds rather than minutes.
The audio is the one part that is encoded, because a new track has to be written. On the free plan it is exported at 44.1 kHz and 192 kbps, which is transparent for music on almost any playback system; Pro exports at 48 kHz and up to 256 kbps. The output container is offered only when it can carry your video as it is. A container that would force a re-encode of the picture is shown as unavailable, with the reason.
This is also why the tool cannot bring old audio back afterwards. Replacing removes the original track from the exported file, so keep your source video. If you might want the old sound later, choose Mix with the original turned down rather than Replace.
Music rights: the part a tool cannot solve
Adding a commercial song to a video is technically easy and legally a separate question. When you add music inside TikTok, Instagram or YouTube Shorts, you pick from a library the platform has licensed for use on that platform. When you add a song to the file yourself and then upload it, you are responsible for having the right to use it. YouTube's Content ID and similar systems routinely detect commercial recordings and may mute the video, block it in some countries, or send the advertising revenue to the rights holder.
- Safest: music you made, or royalty-free music whose licence covers your use, including any commercial use.
- Platform libraries: YouTube's Audio Library offers tracks that are free to use on YouTube; read each track's attribution terms.
- Posting to a social app? If you want a trending sound, add it in the app itself, where the platform's licence applies.
Limits on the free plan
Free handles one video at a time, up to 200 MB and 10 minutes long, with a soundtrack of up to 50 MB — roughly an hour of MP3. Pro removes those numbers, so the limit is what your device can handle, and lets you queue up to 20 clips with one soundtrack and download them together as a ZIP. That is useful for a series of short clips that should all share the same music bed.
If your video is larger than the free limit, either trim it to the part you need or compress it first. If you have photos rather than a video, the image-to-video tool builds the slideshow and adds the soundtrack in one step — see how to make a video from photos. And to take the sound off a clip without adding anything, removing audio from a video is a separate, faster job.
Frequently asked questions
How do I add music to a video for free?
Open the replace-audio tool, add your video and the song, choose Replace or Mix, set what happens if the lengths differ, then export. One clip at a time is free, up to 200 MB and 10 minutes.
Can I keep the original sound and add background music?
Yes. Choose Mix instead of Replace. The video's own sound stays and the music plays underneath at the level you set. For music under speech, start the music at about 30%.
Will adding music reduce my video quality?
No. The picture is copied into the new file without being re-encoded, so it is identical to the original. Only the new audio track is encoded.
What if the song is shorter than the video?
Choose Loop to fill and the song repeats until the video ends. Add a one- to two-second fade-out so the loop does not stop mid-bar.
What if the song is longer than the video?
With Loop to fill or Play once, the song is cut where the video ends. Choose Cut video to audio if you want the whole song and are happy for the video to end with it. You can also set start and end points to use only part of the song.
Can I add copyrighted music to my video?
The tool will add any audio file, but using a commercial song in a video you publish needs a licence. Platforms such as YouTube detect copyrighted recordings and may mute or block the video. Use your own music, properly licensed royalty-free tracks, or the platform's in-app music library.
Which video and audio formats work?
Video: MP4, MOV, WebM and MKV. Audio: MP3, WAV, M4A, AAC, OGG and FLAC.