It's a fundamental notion of arranging and orchestration that any group of musicians can (and often should) be subdivided into smaller groups. Common groupings include the rhythm section, the horn section, the string section, background vocals, and so forth. Each section has its own collective individuality, tending to enter and leave the arrangement together, follow the same dynamics, and play either unison or harmonized parts of the same lines.
Mixing, as the progeny of arranging and orchestration, also deals with groups of tracks. The dozen or so tracks that comprise a typical drum kit are commonly grouped so you can treat them as the single musician they represent. Similarly, you might group several background-vocal tracks for processing with the same delay and reverb.
The term group is used in mixing to mean two different things. A fader group simply gangs the faders and other channel controls of selected tracks together so that moving one moves the rest. An audio subgroup (or just subgroup) routes the outputs of selected tracks through a common bus, returning them to a single track for manipulation and processing (see “Step-by-Step Instructions” for creating a subgroup in Cakewalk SONAR). Either a fader group or a subgroup can thus control the collective volume of a set of tracks, but you can also use a subgroup to process the tracks as a unit and then print them.
One common use of audio subgroups is to organize numerous tracks by bringing them all under the control of a few returns. In a musical context this is often called a submix, whereas in film and video work it's more often called a stem, but this distinction is not dogmatic.
FIG. 1: Here, multiple tracks of dialog, music, and effects are made into subgroups (stems) to organize the session and make it more manageable.
By routing music, effects, and dialog each to its own stem, you greatly simplify making changes to the overall balance of these three groupings at the final mix (see Fig. 1 ). Because all of the source tracks are still available, you retain the ability to go to any individual track and make an adjustment. You can route subgroups to other subgroups, too. The effects stem might be made up of large and small effects subgroups; large effects might include explosions, wind, traffic, etc.
You can use the same technique to print submixes. In SONAR, choose the desired bus in the Export Audio dialog box. In Digidesign Pro Tools, simply route the bus to an audio track and record it there. (See Web Clip 1 for more on stems and submixes in Pro Tools.) You can recombine the resulting files in a new session to reduce track count. Some engineers like to take such submixes — typically at least drums, guitars/keys, and vocals — to the mastering engineer to guarantee greater flexibility with any balance problems. Be careful, however, to include effects returns such as reverb and delay when printing submixes.
When working with insert effects such as dynamics processors (as opposed to send/return effects like time-based processors), use a subgroup to combine multiple tracks on a single track that you can compress with one plug-in instance. With a multitrack drum kit, for example, compressing each track individually lets you shape and control them, but reigning in the kit requires that the threshold of a single processor analyze the kit as a whole.
There are different schools of thought regarding whether to include the overheads and room mics in the subgroup. If you do, you'll have even more room sound in the mix when the kit is compressed. Some engineers do that to compensate for a particularly small or dry drum room. Omitting them from the subgroup lets you leave them uncompressed for a more natural sound or squash them extra hard for a more dramatic effect.
If I don't have time to double-track a horn section, I will sometimes subgroup the horns to two identical returns (buses in SONAR, auxes in Pro Tools) to create a mult. I then either delay one copy slightly or process them differently (using EQ, tape sim, or another timbral effect) and then pan them to opposite sides. Because Pro Tools features independent left- and right-pan on stereo tracks, I will sometimes flip the orientation of one aux track, so the left-right order of the horns on the left side of the mix is right-left on the right side. The net effect is of a larger, thicker section that is present in both speakers but doesn't clutter the middle of the mix. Try this technique on background vocals or strings.
It's not that often that you find a tool that both makes your job more manageable and gives you more creative options, but subgroups are like that. Once your left brain has the basic procedures down, your right brain will start seeing more and more imaginative ways to apply them.
Brian Smithers is Department Chair of Workstations at Full Sail University and the author of Mixing in Pro Tools: Skill Pack from Cengage Learning.
STEP-BY-STEP INSTRUCTIONS ON NEXT PAGE
Step 1: Create a new stereo bus and name it for the subgroup.
Step 2: Select all tracks to be included in the subgroup.
Step 3: Click on the output selector of one track and choose Selected Track Outputs.
Step 4: Choose the new bus and click OK.
Step 5: To process the subgroup, insert a processor in the FX Bin of the bus.
Step 6: :To mult the subgroup, create a new post-fader send. It will be created on all selected tracks. Right click on the pan widget and choose Follow Track Pan.