Add Audio to Video
Add audio to video — lay a music bed, voiceover or sound effect under your clip while the picture stays untouched.
- Free to start
- No re-encode of the picture
- No watermark
Four tracks people lay under a clip
Adding audio to video is nearly always one of four jobs. Knowing which one you are on tells you whether to keep the original sound, replace it, or start from a muted picture.
Add a music bed
Drop a song or instrumental under a montage, a product reel or a b-roll cut. Set the level so the bed sits under the picture rather than fighting it, and loop it to the clip's length.
Add a voiceover or narration
Lay a recorded voiceover over an explainer or a walkthrough. Clearing the location sound first gives the read a clean bed, so the narration is the only voice the viewer hears.
Add sound effects
Put a whoosh, a click or an ambience under a specific moment. You place the effect where it belongs and set its volume against whatever else is playing under the picture.
Replace the original audio
Swap the sound that came with the clip for a new track entirely. The old audio stream is dropped and yours is laid in its place, while the picture carries on untouched.
Bring your track and lay it under the picture in the browser.
Add Audio to Video freeWhat actually happens when you add audio to video
This is where a track-layering tool and a full timeline editor quietly part ways — and why the picture survives when you only touch the sound.
What Pixazo does here
An MP4, MOV or WebM file is a container — a wrapper holding separate streams side by side. Inside sit the picture (encoded with a video codec such as H.264 or HEVC) and usually one audio stream (AAC in an MP4 or MOV, Opus or Vorbis in a WebM). To add music to video, Pixazo writes your new audio into that wrapper and either drops the clip's original audio stream or keeps the picture muted underneath it.
Because only the audio stream changes, the encoded video packets are muxed — copied across into the new container byte for byte — rather than decoded back into frames and re-compressed. That copy is what people mean by a remux, and it is why there is no generation loss: same resolution, same frame rate, same bitrate, the same pixels you shot. Your track is looped or trimmed to the clip length and set to the volume you choose, and its own codec (an MP3 or WAV you brought) is written in as AAC so it plays anywhere the video does.
A re-encode of the picture is only forced when the frames themselves have to change — a new resolution, a trim, a filter, a different video codec for the target container. None of that happens when you are only laying a track underneath, so the picture is copied, not re-rendered.
What a full timeline editor does
A timeline editor lets you stack several stems, automate volume across the clip, cut the picture, and mix a bus down from many tracks. That power comes at a cost: most editors re-encode the whole video on export, so a second lossy pass costs a little detail.
If the whole job is "put this one track under this clip", that heavier workflow is more than you need. Laying a single track and muxing the picture through is cheaper, faster and more faithful to the original frames.
What you can lay under a clip
Whatever you drop in is written into the container as one audio stream, but the four kinds behave differently once they are under the picture. Knowing the differences tells you what to set — the level, the start point, and whether to keep or drop the original sound.
A music bed under the whole clip
A song or instrumental that runs the length of a montage, a product reel or a stretch of b-roll. If the track is shorter than the clip it is looped back to the top; if it is longer it is trimmed to the out-point, so it never cuts off early or overruns the last frame.
- Loop or trim so the bed matches the clip length exactly
- Set the level manually so the bed sits under the picture, not over it
- Duck it yourself by a few decibels wherever a voice or effect needs to be heard
A voiceover or narration on top
A recorded read for an explainer, a walkthrough or a piece to camera. You align it to the start point where the speech should begin, and you decide whether to keep the location sound quietly underneath it or drop it entirely.
- Align the read to the moment on screen it belongs to
- Keep the original sound as a faint bed, or drop it for a clean read
- Pair it with a ducked music bed so the voice stays intelligible
Sound effects and stingers
A single whoosh, click, riser or logo stinger placed at one specific moment rather than across the whole clip. You choose where it lands and set its volume against whatever else is already playing under the picture at that point.
- Place the hit at the frame the action calls for
- Balance its level against the bed and any voice
- Use short one-shots — this lays a track, it does not build a full mix
Ambience and room tone
A steady bed of atmosphere — rain, a cafe, a room's own quiet hum — that fills the silence when the original sound is gone or thin. It loops to length like a music bed and sits low, so it reads as space rather than as a sound you are meant to notice.
- Loop a seamless atmosphere to the full clip length
- Hold it low so it fills silence without drawing attention
- Layer it under a voiceover to stop a clean read sounding dead
Music, voice, an effect or a wash of ambience — bring the file and lay it under.
Add Audio to Video freeFormats, files and what comes out
The tool reads the container to see what streams are inside rather than trusting the extension. Here is what it accepts on the way in and what you get on the way out.
| Video containers that take a new track | MP4 and MOV are the everyday cases, and WebM works too. Each is a wrapper that already carries a video stream, so a fresh audio stream is written straight in alongside it. |
|---|---|
| Audio files you can bring | Common audio files work as the track you lay on — MP3, WAV, AAC and M4A. You supply the file; the tool does not generate music or a voice for you. |
| How the audio is written in | Your track is encoded to AAC inside the new MP4 or MOV so it plays everywhere the video plays, and it is looped or trimmed to the clip length at the level you set. |
| Typical output | An MP4 with your track under the picture, at the same resolution, frame rate and length as the clip you brought — the picture is muxed through, never re-encoded. |
| Phone support | Pixazo runs in the browser on desktop and mobile, so you can score a clip on the same phone that shot it, no app to install. |
| Watermark | No watermark is burned onto the picture. Adding a track changes the sound, not the frames. |
Bring an MP4 or MOV and an MP3 or WAV, and keep the picture exactly as it was.
Add Music to VideoHow to add audio to a video in four moves
The whole flow runs in Pixazo in the browser. Nothing to install, and these four moves are the entire job.
Upload the video you want to score
Sign in and drop your clip into Pixazo. MP4, MOV and WebM are the everyday cases, and the tool reads the container to see what streams are already inside. The picture stays exactly as you shot it, because only the audio stream is going to change.
Add your audio — music, voiceover or SFX
Bring in the track you want to lay under the picture: a music bed, a recorded voiceover, a sound effect or a wash of ambience. Common audio files such as MP3, WAV, AAC and M4A work, and you supply the file — Pixazo lays it onto the clip rather than generating it for you.
Set the start point, volume and loop or trim to fit
Choose where the track comes in, set its volume against the picture, and loop or trim it so it runs the exact length of the clip. Decide whether to drop the original sound and replace it, keep it quietly underneath, or score a muted picture from silence.
Render and download the scored clip
Render the clip with its new track, play it back to check the levels and the start point, then download. When only the audio changed, the picture is muxed through untouched — same resolution, same frame rate, no watermark.
Lay a music bed, a voice or an effect and keep the frames exactly as they were.
Add Music to VideoAdd audio here, or edit in a full timeline?
Both put a track under your clip. They are not the same job, and picking the wrong one either costs you quality or costs you an afternoon.
| What matters | Lay a track here | Full timeline editor |
|---|---|---|
| The job it fits | Put one music, voice or SFX track under a clip | Stack, cut and mix many tracks over a full edit |
| Picture quality | Muxed through — not re-encoded, so no loss | Usually re-encoded on export, a second lossy pass |
| Speed | Fast — only the audio stream is written | Scales with the length and the number of layers |
| Beat-match and sync | Manual — you set the start point yourself | Frame-accurate control across the timeline |
| Multitrack mixing | One track under the picture, not a mixdown | Full stem mixing and volume automation |
| Best for | Music beds, voiceovers, quick SFX, swapping the sound | Edits where the picture and several stems both change |
If the job is one track under one clip, this is the faster route.
Add Audio to VideoWhat this add-audio tool will not do
The operation is deliberately narrow. Being straight about the edges saves you a wasted upload.
It does not beat-match or auto-sync
It lays your track under the picture at the start point and volume you set. It will not align musical hits to a cut or move the beat to the action — that timing is a manual, editorial choice.
It does not lip-sync
Dropping a voice track over a face does not make the mouth match the words. Generating lip movement to fit a voiceover is a different class of tool entirely.
It lays one track, not a mix
This is a track-layering tool, not a multitrack mixing desk. It puts a single track under the picture; it will not mix a bus down from several stems or automate levels across the clip.
It will not clean your audio
There is no noise reduction, de-hum or levelling. It lays the file you bring exactly as it is, so clean or repair the track before you add it if it needs work.
It does not generate music or voices
You supply the audio file. It does not compose a track or synthesize a voice for you — it lays the music, voiceover or effect you already have onto the video.
It does not edit the picture
This changes the sound, not the frames. It will not trim, cut or re-order the picture; for that you want a timeline editor, and the trade-off is a re-encode on the way out.
Short version: if your sentence is "put this track under this clip", you are in the right place. If it continues with "and cut the picture to it" or "and make the mouth match", that is a timeline editor or a lip-sync tool.
Questions about how to add audio to video
Is it free to add audio to video with Pixazo?
You can start for free without a credit card. Heavier use runs on the same credit system as the rest of the platform, and current allowances are listed on the pricing page.
Does adding audio re-encode the video?
No. When only the audio stream changes, the picture is muxed through into the new file without being re-encoded, so there is no quality loss — same resolution, same frame rate.
Can I replace the original sound with a new track?
Yes. You can drop the clip's existing audio and lay your new track in its place, or keep the picture muted and score it from silence. Either way the new track becomes the audio you hear.
Can I set the volume and loop or trim the audio to fit?
Yes. You set the new track's volume against the picture, choose where it starts, and loop or trim it so it runs the exact length of the clip rather than cutting off early or overrunning.
Which audio and video formats can I use?
MP4 and MOV are the everyday video cases, and common audio files such as MP3 and WAV work as the track you lay on. The engine reads the container to see what streams are inside.
Can I add a voiceover or narration over the clip?
Yes. A recorded voiceover is just another audio track — bring the file in, set its level, and it plays over the picture. Clearing the original sound first gives the narration a clean bed.
Does it beat-match or sync the music to the action?
No. It lays your track under the picture at the start point and volume you set; it does not auto beat-match or align musical hits to on-screen movement. Timing the cut to the music is a manual, editorial job.
Can I add audio to a video on my phone?
Yes. Pixazo runs in the browser on desktop and mobile, so you can score a clip on the same phone that shot it.
Does it generate music or voices for me?
No. This is a track-layering tool, not a generator — you bring the audio file. It lays the track you supply onto the video; it does not create music or synthesize a voice for you.
Can I set where the music starts?
Yes. You choose the start point where the track comes in, so the music, voice or effect begins on the frame you want rather than always from the top of the clip.
Can I lower the music under a voice?
Yes. You set the music bed's level by hand, so you can duck it a few decibels under a voiceover to keep the read clear. It is a manual level you choose, not automatic ducking.
Will my video get a watermark?
No. Adding a track changes the sound, not the frames, so nothing is burned onto the picture. The clip comes out at the same resolution and frame rate with no watermark.
Does it change the video resolution or length?
No. The picture is muxed through untouched, so the resolution and frame rate are unchanged, and the output runs the same length as the clip you brought — your track is looped or trimmed to fit it.
Free to start, runs in your browser, no watermark.
Add Audio to Video freeDeepak Joshi is a Content Marketing specialist having a combined experience of 10+ years working in the digital world. He is one of the active contributors to Pixazo Blog and has keen interest creating and marketing content related to AI tools, No-Code technology, Design Industry, Social Influencers, and other trending topics. A health and sport enthusiast, Deepak loves to indulge in all kinds of sports & games.
