Watch the same ten seconds of video three times, silent, then with music, then with music and a voice. What changed?

1. No sound

2. Music

3. Music and a voice

Video: "Dublin snow benburb st", via Wikimedia Commons, free for anyone to use (CC0). The narrator is made up for this lesson.

Today you will edit one messy recording into a clean thirty second clip.

Almost every piece of digital media uses three kinds of sound, often at the same time.

• Voiceover is someone speaking to explain or tell the story, and it carries the information.
• Sound effects are short sounds like a door creaking or a notification. They make things feel real and show that something happened.
• Music is the background track, and it sets the mood before anyone says a word.

Think about the last short video you watched. Which of the three did you notice, and which did you not notice at all?

AudioMass is a free audio editor that runs in your browser. Open it at audiomass.co. Make sure the address ends in .co, because audiomass.com is a different site full of adverts.

Follow the steps below to open it and load the practice clip you downloaded. The green shape you will see is called a waveform, which is a picture of the sound. Tall parts are loud and flat parts are quiet.

The practice clip starts with about eight seconds of a creaking door before the music begins, and it goes on too long at the end. Neither part belongs in a finished clip.

Trimming takes two moves. First you select the part you do not want, and then you cut it. Everything after a cut slides left to fill the gap.

A clip that starts at full volume sounds like a mistake, and one that stops suddenly sounds unfinished. A fade fixes both problems.

A fade in brings the sound up slowly from silence over the first few seconds, and a fade out brings it back down at the end. Watch how the shape of the waveform changes when you add each one.