Sound Track: Multi-track Audio for Video

When you have a video production that begs for creative, high-impact audio, the limited audio abilities of your camcorder may not cut it. To put together the soundtrack you know your video production deserves, you may need a multi-track audio recorder. Modern audio/video post-production is totally dependent upon multi-track recorders to layer up a number of audio tracks. You can do this as well, using techniques like "bouncing tracks" or "sound-on-sound" to provide professional audio-for-video when a limited number of tracks are available on your machine.

A multi-track recorder allows you to individually record, re-record, modify or erase a number of audio tracks that are perfectly in sync with each other. Afterwards you can combine or "mix" the multiple tracks into your high-impact mono or stereo soundtrack.

The latest software-based multi-track audio systems use a hard disk as the storage medium. These systems are becoming more common and less expensive, making them the wave of the future for multi- track audio. Their flexibility makes the job of producing complex audio soundtracks even easier. It's like putting a puzzle together one piece at a time until the whole picture emerges.

Putting the Pieces Together

Once you understand the concept of multi-track audio recording, the process of putting together a multi-track audio soundtrack is not hard. In fact, it's as easy as 1, then 2, then 3..., right on up to the limits established by the number of tracks you have to work with.

If you are using time code or MIDI to keep both your video machines and audio tracks in perfect synchronization, you might start with a sync track. More commonly, you are operating on a budget, and you will start by dubbing the audio track from your camcorder onto one track of the multi-track recorder. Other times you may just want to narrate a video clip, or maybe you want to look at the video and create original music or sound effects to enhance the visual images. The choice is yours.

You "lay down" the first track by putting that track number on the recorder into the record mode. After that, you just go to the next track number on which you wish to record a signal and put that track into the record mode. By putting another track into the record mode, the machine will automatically switch into the sync mode, assuring that your subsequent tracks are in sync with the previous tracks.

A typical audio-for-video soundtrack might include music, narration and sound effects. You can weave the various elements of the audio track in and out as is appropriate for the production by controlling the various individual audio tracks during mixdown with your audio mixer.

Mixdown

The mixing console is a device that lets you be creative in combining the individual audio tracks you recorded earlier. Small four-track cassette multi-track machines will usually have a built-in mixer that allows you to mix the tracks right on the machine. These machines range from very basic, with a barely functional mixer, to quite elaborate, with a high-tech mixer whose function and abilities make the unit a mini-studio in a box. Cassette four-track machines are still the least expensive way to begin doing multi- track audio production.

Once you jump up into eight tracks or more, you will need a mixing console. This is true with either the analog or digital multi-track machines, though a few hard disk recorders do have built-in mixers or mixing software for use with a computer. The console allows you to input microphone signals and line- level signals (from camcorders, CDs and other sources) and mix them onto the multi-track. When you have all the tracks you need on the multi-track, the console then serves to do the mix, combining the individual tracks into one audio soundtrack.

If you are working with a limited number of tracks, you can "bounce" them to free up room. With a four-track machine, for example, you can combine (mix) three tracks to the blank fourth track, leaving the first three tracks available for more audio signals. Once you do the bounce, you can't change the relative mix of the elements--they're combined for good as soon as you erase and reuse the first three tracks. This technique gives you six tracks of audio from your four-track machine. You could bounce again for even more tracks, but the audio quality begins to suffer on analog machines as each bounce puts you another generation away from the original signal. Noise builds up with each generation, because the audio signal carries a certain amount of tape noise.

A better way to squeeze in another track is to do "sound-on-sound" while mixing the first three tracks to the fourth. As you do the track combining mix, you can also mix in another original audio signal at the same time. This audio signal merges with the signals from the first three tracks, hence the term "sound-on-sound."