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.
Audio 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

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.

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.

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.