Paying close attention to the sound and music of your video is crucial. Poor sound in a video is a huge distraction for the viewer. Fortunately for us, iMovie gives us some tools so that we can completely avoid this scenario. The first thing we want to do is make sure the audio level (or volume) of each clip is right. To adjust the audio level of a clip, mouse over the clip in the timeline to reveal the gear icon, click on the gear icon and select audio adjustments. From there you can adjust the volume of clip as well as set fades and a variety of other adjustments.
Then there’s music. Music does a great job setting the mood you want for your video. To add music, click the music icon below the viewer, which will open your Music and Sound Effects libraries on the right side of the screen. There you can choose from the iMovie and iLife Sound Effects folders as well as GarageBand and iTunes. Once you’ve found the piece of music or sound effect that you’re looking for, drag it into the timeline. Adjusting the audio clip is similar to adjusting the audio on a video clip. Simply mouse over the audio in the timeline, and click on the gear icon and select Audio Adjustments. Trimming audio clips is also easy. To do so, mouse over the clip and click the gear icon and select Clip Trimmer. The clip will then open up in the Event Library window where you can trim the audio by dragging on either of the highlighted ends.
Continue on to Transitions & Effects.