Sound Advice: It's All in the Mix

Hal Robertson
June 2007

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Mixing audio is all about balance: balance between individual elements and between the music, sound effects and dialog. There's even a balance between edited takes of the same scene.

To use a food analogy, the average person might put a collection of foods in a blender and pulverize the whole thing. On the other hand, a chef will carefully fold ingredients together, paying close attention to quantity and order. The difference in the results should be obvious. Most people grasp one mixing discipline better than the other, but knowledge of both will help make better mixes.

If you've never mixed audio for video the old-school way, it's easy to take our modern conveniences for granted. Here's how it used to work. The project was shot and edited on tape - analog tape. No computers or FireWire, just thin bands of magnetic tape in chunky video decks.

The editor would scrub through the raw footage by hand, assembling an edit on another video deck one real-time piece at a time. That was fine for a basic edit, but what if you wanted to include a voice-over, background music or sound effects? Most editing decks allowed you to overdub audio on one of the two, three or four channels available. This was a hit-and-miss affair. If you got it wrong, you did it again till it was right (or you gave up). If you actually wanted to mix the audio, it got recorded on an analog multitrack deck. You built elements on the tracks and mixed them by memory, making fader and knob moves in real time. When it was time to make the master, both the audio and video decks were synced with timecode and, if all went well, the final version was recorded. If this sounds incredibly complicated, it was, but it was the only way to get the job done. Only the mega-studios and production houses had automated mixing.

Today, everyone has access to automated mixing. Depending on your audio and video software, you can easily accomplish static and dynamic mixes and save them with your project. It's simple to manage multiple audio tracks along with their associated plugins, volume and pan settings. Everything stays exactly where you put it, and it will be that way tomorrow, next week or next month. These powerful features remove much of the worry and difficulty of mixing audio for video. That leaves you with more time to concentrate on the sound of the mix.

There are several ways to mix audio for your video projects. Your video editing app likely offers two or three methods. The first (crudest) way is to normalize track volumes to something other than optimum. Most video editing apps allow you to normalize an audio track to some arbitrary amount of boost or cut. If something is too loud compared to the other items in the mix, simply normalize 3-6dB lower than your current setting. Admittedly, this is a quick and dirty method, but it offers quick results. A second (more elegant) method is the built-in mixer utility. Some programs offer volume adjustment on the timeline, while others use a separate mixer window. Regardless, this method looks and acts like a real mixer and allows adjustments to all the audio tracks in your project. The final mix method requires setting markers or keyframes at specific points in your mix and drawing volume changes. This can be done over broad areas or in very small instances. You can also set points as necessary to achieve a quality mix.

Alternatively, you can mix in an audio-only package and export the results to the timeline. This requires exporting any audio you need from your timeline and then importing it into the audio software. Add other audio elements on their own tracks for maximum control. Now you can use any of the mixing tools from the audio application to craft your soundtrack. This includes the mixer, automated fades, mutes and audio-specific plugins. Once the mix is complete, export the soundtrack and import into your video editing app, making sure to mute any original tracks. If you're using Adobe Production Studio products Premiere Pro and Audition, you can even import the session file from Audition and go back to make tweaks as needed. [Editor's note: Audition will be replaced by Soundbooth in the Adobe Production Studio. At time of publishing, however, Soundbooth was still in beta.]

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