Mute & Add Audio: Mastering Video Audio Tracks

Muting isn't just "setting the volume to zero," and scoring isn't as simple as layering music on top. When two audio tracks mix, which "volume layer" should voice and music each occupy?

Audio Tracks in Video

A video file typically contains at least two data streams: a video stream and an audio stream. The audio stream records the sound information in the video, including speech, music, and ambient sounds. Understanding audio tracks is the foundation for audio operations.

Basic Audio Track Properties

Muting: Removing Sound from Video

What Is Muting?

Muting removes the audio track entirely from a video, producing an output with only visuals and no sound. This is different from turning the volume to zero—muting physically deletes the audio data, while volume adjustment only reduces playback loudness.

Why Mute?

• Replace audio: Remove original sound to add new background music or voiceover.
• Eliminate noise: When original audio quality is poor (wind, ambient noise), removing it is simpler and more effective than noise reduction.
• Social media norms: Some platforms autoplay videos with sound off by default; proactively muting avoids embarrassing content being accidentally played with sound.
• GIF-style video: Silent short videos are widely used on social media for pure visual expression.
• Copyright avoidance: Original video music may have copyright issues; removing it allows safe reuse.

Impact on File Size

Removing the audio track typically reduces file size by 10%-20%. For videos with low video bitrate, audio may account for a larger proportion, and the size reduction after muting is more significant.

Adding Music: Giving Video a Soul

The Role of Background Music

Music is the core element of emotional expression in video. The same footage paired with different music can convey entirely different emotions:

• Upbeat music → Light and cheerful
• Tense drums → Suspense and excitement
• Soft piano → Warm and touching
• Epic orchestral → Grand and magnificent

Audio Mixing Concepts

When adding music to a video that already has audio (speech, ambient sound), you need to mix the two audio tracks:

• Original audio: Preserve speech and ambient sound, usually at unchanged or slightly reduced volume.
• Background music: Added music, usually lowered to 10%-30% of the original audio's volume, serving as accompaniment without overpowering.

Mixing considerations: - Music should not overpower speech; vocal clarity takes priority. - The music's rhythm and mood should match the visual content. - Volume changes should transition smoothly, avoiding sudden jumps.

Audio Fade In and Fade Out

• Fade In: Music gradually increases from silence to target volume, avoiding the jarring impact of sudden sound.
• Fade Out: Music gradually decreases from target volume to silence, avoiding abrupt cutoff.

Fade durations are typically 1-3 seconds, depending on the music's style and rhythm.

Ducking: Automatic Volume Courtesy

In videos with voiceover, the professional technique is ducking (also known as sidechain compression): whenever speech is detected, the background music automatically dips by 6-12 dB; when the speech pauses, the music gently swells back. This preserves the music's atmosphere while keeping voices clearly intelligible—a standard technique in podcasts, vlogs, and advertising. To duck manually, split the music at each speech segment and set a lower volume for those portions.

Loudness Matching: The Groundwork Before Mixing

A video's original audio and the music you want to add are rarely "born equally loud": mix them directly, and either the music buries the voice or the voice feels pasted on. The correct order is:

1. First match the loudness (not the peaks) of both tracks to a similar level;
2. Then position the music below the voice as accompaniment (roughly 10-20 dB lower);
3. Finally, check that the overall output loudness meets your target platform's standard (around -14 LUFS for video platforms).

For the principles behind loudness and LUFS, see this series' article Volume, Gain, and Loudness.

Layering in Multi-Track Mixing

When mixing more than two audio tracks, you need to think in terms of foreground, midground, and background layers. A typical video soundtrack has three layers:

The three layers avoid "fighting" through frequency separation: the midrange of speech (roughly 300 Hz – 3 kHz) must stay clear, while background music can be gently scooped in that band (EQ sidechain) so the voice "cuts through." This is the core concept of frequency masking in professional mixing — when two sounds occupy the same frequency range, the ear struggles to tell them apart.

Matching Audio and Video Duration

When the added music is longer than the video, the usual approach is to trim the music to match the video length. When music is shorter:

• Loop the music (may create noticeable repetition)
• Only play music for the portion that has it, leaving the rest silent
• Choose longer music material

Common Audio Formats

A Practical Guide to Music Copyright

When adding music to a video, copyright is the most easily overlooked yet most consequential issue. Here are the most practical principles:

What Music You Can Use

The Most Common Copyright Myths

1. "I bought the song on a music platform, so I can use it in my video": What you purchased is a personal listening right, not the synchronization license (sync license) needed to pair music with video. Using a song from Spotify as your video's background music is infringement.
2. "It's fine as long as I credit the source": Copyright is a matter of permission, not attribution. Using music without a license is infringement even if you credit the source.
3. "Other people on YouTube use this music, so I can too": Others using it doesn't grant you the right, and platform content-identification systems (Content ID) will scan your video independently.
4. "Clips under 30 seconds are fine": There is no "short clip exemption" in copyright law; rights holders can still assert their claims.

Safe Choices

• Personal, non-profit videos: choose CC0 or CC BY licensed music
• Commercial videos: subscribe to a royalty-free music library (e.g., Epidemic Sound, Artlist) — typically a couple hundred dollars a year, far less than a single infringement claim
• Voice-only content (podcasts, tutorials): use AI-generated background music (e.g., Mubert, Soundraw) — you own the rights to what these services generate
• The safest option: compose your own or commission original music

Practical Tips

• Backup before muting: Muting is irreversible; ensure you have the original file backed up.
• Music copyright: Prefer CC0 or commercial royalty-free libraries; never use popular songs.
• Volume balance: Listen after adding music to ensure speech is clear and the music doesn't intrude. The voice should always be the most prominent element in the mix.
• Fade in/out: Always add fades to added music for a smoother listening experience. A 1–2 second fade-in and 2–3 second fade-out work well.
• Format choice: Prefer AAC or MP3 for added music to ensure compatibility. Avoid lossless formats like WAV for background music — the file grows significantly while the quality gain is barely perceptible in a background layer.
• Check on multiple devices: Test your mix on different devices (phone speakers, headphones, computer speakers). Background music can bury the voice on phone speakers, so verify vocal clarity on a phone speaker before publishing.

Related Tools

• Mute Video
• Add Audio
• Audio Volume