Track Bouncing Basics

Bouncing can go beyond track “freezing”

By Craig Anderton

In the days of four-track tape recorders, one of the tricks that made decent multitracking possible was bouncing, where you’d mix three of the tracks down into the fourth. You could then erase the three original tracks, and record three more in their place. Noise? Distortion? Yes, but it was all we had.

Bouncing’s legacy lives on in track “freezing,” which essentially bounces the audio from a soft synth into a hard disk audio track instead of playing back directly from the instrument. This saves CPU power because it takes less juice to play a hard disk track than perform a zillion real-time calculations to approximate the sound of, say, a vintage Minimoog.

But bouncing has other uses, too — and that’s what this article is about.

HOW TO BOUNCE

Hard disk recording programs implement bouncing in different ways, but the basic principle is the same. Note that if the track being bounced includes plug-in processors, their sound will be part of the bounce unless you can specify otherwise; and if you bounce multiple tracks, they’ll likely mix together.

1. Mute any track or bus that’s not supposed to be bounced. Note: if you’re “bouncing” a soft synth track to turn it into audio, you may need to bounce the MIDI track driving the soft synth as well as the soft synth audio output.

2. Select the section you want to bounce. Generally, the more you’ve selected to bounce, the more time it takes to calculate and execute the bounce. There’s no need to bounce the entire track if you need to bounce only a section.

3. Play back what you’ve selected and observe the track’s meters (or bus meters, if that’s where the bounce is coming from). Check that there’s no clipping; otherwise, trim levels as necessary prior to bouncing.

4. Read any documentation to determine the available bounce functions. Generally, you’ll have two options: Bouncing creates a new hard disk audio track, or it exports the track to an audio file, which you can then import into the program.

5. Initiate the bounce.

6. Play back the bounced track to make sure there aren’t any glitches, overloads, etc.

BOUNCING APPLICATIONS

Now that you know how to bounce, here are two very useful applications.

Back up soft synth parts. When backing up a project, rendering a soft synth to a audio file via bouncing (Fig. 1) provides a “safety net” if you need to call up a project in the future, and for some reason (e.g., lack of compatibility with a newer operating system) you can’t load the soft synth. If you’ve inserted a plug-in processor after the soft synth, consider bouncing two versions—one with the effect, so you can reproduce the sound as planned, and one without in case you want to change the effect later.

Fig. 1: A track is being bounced in Cakewalk Sonar, which gives the option to turn several parameters on or off during the bouncing process. Here, Track FX are enabled so that any effects are part of the bounced sound; however, you might want to create a second backup track without effects—just in case.

The “backwards tape” effect. To resurrect this classic effect, duplicate the track to which you want to add reverse processing, then reverse this copy (look for reverse under a program’s DSP menu). Next, bounce the reversed track through reverb (no dry sound, only processed) to another track. Delete the copied/reversed track; it’s not needed any more. Finally, reverse the reverb track that was bounced, and make sure it lines up with the original track. Don’t forget you can get creative with the reverb track—pitch shift it, slide it forward or backward in time to line up correctly (or incorrectly), and so on.

Create a stereo master. Bounce everything down to two tracks, and voilà — there’s your final mix. So why not just export to an AIFF or WAV file? You can, and eventually will. But there’s an advantage to this approach. Suppose you listen back to the track, and decide the piano needs to come up a tiny bit in one section. Rather than start over from scratch or mess with automation, just set the piano level as desired, select the region where you want the piano, and bounce just that section into the track with the final mix. The splice points should be sample-accurate, so you should hear no click or transition as the old mix transitions into or out of the new section, unless level changes occur in the middle of a note.

Craig Anderton is Editor Emeritus of Harmony Central. He has played on, mixed, or produced over 20 major label releases (as well as mastered over a hundred tracks for various musicians), and written over a thousand articles for magazines like Guitar Player, Keyboard, Sound on Sound (UK), and Sound + Recording (Germany). He has also lectured on technology and the arts in 38 states, 10 countries, and three languages.