Free Auto-Ducker & Sidechain Tool

Mix a voice recording with background music: the music is turned down automatically whenever the voice speaks and comes back up in the pauses.

Online Podcast Audio Mixer

Open a voice track and a music track, choose how far the music should drop, and download the finished mix as a WAV file. Both files stay in your browser.

What Is Auto-Ducking?

Ducking means lowering one sound whenever another is present. The Auto-Ducker analyzes your voice track and lowers the music whenever the voice rises above the threshold you set, then brings it back when the voice stops. In a studio this is done with a sidechain compressor; the result is the same. The guide How to Mix Vocals and Background Music explains the technique and the settings in detail.

Good Starting Settings

Press Preview Mix and adjust the sliders while you listen:

  • Voice Threshold: start at -30 dB. If the music doesn’t drop on quiet words, lower it; if it drops on breaths or background noise, raise it.
  • Music Reduction: -12 to -15 dB for a podcast, -9 to -12 dB for a lively video.
  • Attack Time: about 50 ms. The music begins to drop just before the voice starts, so the first word isn’t covered.
  • Release Time: about 500 ms. Lengthen it if the music surges between sentences.
  • Music Volume: if the music is much louder than the voice in the pauses, lower it by 6 to 12 dB.

Who Is It For?

Podcasters, YouTubers, audiobook narrators and anyone who wants to put music under a spoken recording without drawing volume changes by hand in an editing program.

How to Use the Auto-Ducker in 3 Steps

Step 1

Open Both Tracks

Choose your voice recording on the left and your background music on the right. MP3, WAV, FLAC and M4A work in all modern browsers.

Step 2

Adjust the Ducking

Press Preview Mix, then set how far the music drops and how quickly it returns.

Step 3

Download the Mix

Click Download Mix (WAV) to save the finished mix to your device.

Select Audio Files

1. Voice Track

Drag and drop your voice recording here or choose a file.

2. Background Music

Drag and drop your music here or choose a file.

Supported formats: MP3, WAV, FLAC, M4A and OGG (OGG depends on your browser).

Ducking Settings

Preview & Export

Music level: -- 00:00 / 00:00
Tip: Use headphones to hear the changes clearly. On a phone, make sure silent mode is off.

The mix is exported as a 16-bit stereo WAV and is as long as the longer of the two tracks. If the peaks would go above 0 dB, the level is lowered automatically to -1 dB.

Tip: Need an MP3? Export a WAV here, then convert it.
WAV to MP3 Converter

Sound Optimizer

Want to adjust the tone or the loudness of the finished mix? The Sound Optimizer has EQ, a compressor and loudness meters on one page.

Frequently Asked Questions

Is the Auto-Ducker tool really free?
Yes. The Auto-Ducker is free to use, with no sign-up and no daily limits. You can mix as many episodes or voice-overs as you like.

Are my audio files safe and private?
Yes. The mixing is done in your browser on your own device. Your audio files are never uploaded to our servers.

What is auto-ducking?
Auto-ducking lowers the background music automatically whenever the voice is speaking and raises it again in the pauses, so the words stay easy to understand.

Is this the same as sidechain compression?
The result is the same. A sidechain compressor lowers one track according to the level of another; the Auto-Ducker analyzes the voice track and lowers the music in the same way, with threshold, depth, attack and release controls.

What are the best settings for a podcast?
Start with a Voice Threshold of -30 dB, a Music Reduction of -15 dB, an Attack Time of 50 ms and a Release Time of 500 ms. Then listen to the preview and adjust: the music should step back without seeming to switch off.

What do the Attack and Release sliders do?
Attack sets how quickly the music drops when the voice starts; around 50 ms is a good start. Release sets how quickly the music returns after the voice stops; around 500 ms sounds smooth, and longer times keep the music from surging between sentences.

Why is the music too loud between sentences?
Music files are often much louder than a voice recording. Lower Music Volume by 6 to 12 dB so the music sits below the voice even when it is not ducked.

What happens if the music is shorter or longer than the voice?
The mix is as long as the longer track. If the music is shorter, it simply ends; if it is longer, it plays on after the voice. You can shorten the result with the Audio Trimmer and add a fade-out with the Audio Fade Tool.

Can I get the mix as an MP3?
The tool saves an uncompressed 16-bit WAV file. To make an MP3, convert it afterwards with the WAV to MP3 Converter.

Do I need to install any software?
No. The Auto-Ducker runs in your web browser on computers, phones and tablets.

Can I use copyrighted music under my voice?
Use music you made yourself, music you have licensed or royalty-free tracks whose license covers your use. Publishing a commercial song under your voice usually requires permission from the rights holder.