Background music needs to sit UNDER whatever's already playing — dialogue, voiceover, ambient sound — not replace it. Versely's attach_audio_to_video tool has a dedicated 'mix' mode for exactly this: it keeps the original video audio and layers new audio on top, with separate volume controls for each.
If you don't already have a track, generate_music writes one from a text prompt first (genre, mood, tempo), then you attach it in mix mode.
Powered by
Attach an audio file to an existing video. Use when the user has a generated/uploaded video AND a separate audio track (music, voiceover, SFX, generated speech) and wants them combined. Two modes: (A) 'replace' (default) — strips the video's original audio and substitutes the supplied audio. Pick this when the user says 'replace the sound', 'mute the original', 'put this music on the video', or any time the supplied audio should be the only audible track. (B) 'mix' — keeps the original video audio AND mixes the new audio on top, with separate volume controls. Pick this when the user wants background music UNDER existing voice/SFX (e.g., 'add background music', 'put music behind my talking video'). Video stream is copied losslessly (no re-encode of visuals). Fast. Costs a flat credit fee regardless of length.
What to tell the agent
Versely's agent maps this plain-English request directly onto attach_audio_to_video. You don't need to know the parameter names — just describe what you want.
“Generate an upbeat lo-fi background track, then mix it under this video at low volume so my voiceover stays clear.”
How it works
1. Generate or bring a track
Describe genre, mood, tempo and instruments to generate_music, or point to an existing track's URL.
2. Choose mix mode
attach_audio_to_video's mode: 'mix' keeps the video's original audio AND layers the new track on top — this is the setting for background music under existing voice or SFX.
3. Balance the volumes
Set music_volume low relative to original_volume so dialogue or voiceover stays intelligible over the bed.
4. Render
The video stream is copied losslessly (no re-encode of visuals) and the mixed audio is returned as a finished MP4.
What it costs
attach_audio_to_video charges a flat credit fee regardless of video length. generate_music is billed separately per track if you don't already have one — ask the agent for estimate_cost before generating.
The formula behind that number: What does an AI video with sound cost? — flips the per-second rate with an audio toggle rather than adding a separate fee.
Limits & things to know
- Use mode 'mix', not 'replace' — 'replace' strips the original audio entirely, which is the wrong setting for background music under existing sound.
- You control relative loudness via music_volume/original_volume, not a full mastering chain.
- If the video has no existing audio worth keeping, replace-video-audio (mode 'replace') is the simpler path.
Who uses this
- Vlogs and talking-head videos that need a bed
- Product demos and ads
- Silent B-roll cutdowns
- Slideshow-to-video exports
Frequently asked questions
Will adding music remove my existing voiceover?+
Not if you use mode 'mix' — it keeps the original video audio and layers the new track on top with separate volume controls. Mode 'replace' is the one that strips the original audio.
Do I need to already have a music file?+
No — generate_music can write an original, royalty-free track from a text prompt (genre, mood, tempo) that you then attach with attach_audio_to_video.
Does adding music re-encode my video quality?+
No — attach_audio_to_video copies the video stream losslessly; only the audio track is touched.
How much does it cost?+
attach_audio_to_video is a flat fee regardless of the video's length. generate_music is billed separately per track generated.
See it in a workflow
Related Versely tools
Related editing jobs
Add Music to a Video inside Versely
The all-in-one AI studio for creators. 60+ models for video, image, voice, music and lipsync in a single app.