> For the complete documentation index, see [llms.txt](https://doc.duaer.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://doc.duaer.com/build/duaer-video-music.md).

# Add background music with Duaer Video Music

In Duaer, Duaer Video Music lays music under the voice of a Duaer video. The music loops or is cut to the video length and fades out. It is free.
## Add music to a video

1. Get the music: generate it with [Duaer Music](/build/duaer-music.md) and set its Output Binary Field to music, or use any node that carries an audio file.
2. Combine the video and the music into one item with [Merge](/integrations/builtin/core-nodes/duaer-nodes-base.merge.md): set Mode to Combine and Combine By to Position, with Duaer Video Render or Duaer Video Concat on one input and the music on the other.
3. Connect Duaer Video Music. Render ID defaults to {{ $json.renderId }} and Music Binary Field to music.
4. Set Music Volume from 0.05 (faint) to 1 (unchanged). The default is 0.3.
5. Select Execute step. The binary field data holds the MP4 with music, plus a new renderId, duration in seconds, and sourceRenderId (the original video).

The music must be an audio file of 10 MB or less. The source video must be under 3 hours old, and mixing waits at most 15 minutes.
## Questions

### Why does Duaer Video Music say "Binary field music is not audio"?

The music field holds no audio, or the item has no music field. Check that Duaer Music writes to the music field and that Merge combines the music and the video into one item by position.

### What does Duaer Video Music do when the music and the video differ in length?

In Duaer, shorter music loops and longer music is cut; either way it fades out at the end.

## Related

- [Generate music with Duaer Music](https://doc.duaer.com/build/duaer-music.md)
- [Render HTML to video with Duaer Video Render](https://doc.duaer.com/build/duaer-video-render.md)
- [Join shots with Duaer Video Concat](https://doc.duaer.com/build/duaer-video-concat.md)