Unison double-tracking of a part is a standard engineering technique, whether for creative purposes (think Beatles) or for corrective purposes (think Paula Abdul). Doubling vocal and instrumental leads makes them sound thicker; doubling rhythm parts, especially guitars, and panning them to different sides of the stereo field makes them present everywhere but in the middle of the soundstage.
FIG. 1: Pitch-correction software, such as Magix Audio Studio''s Elastic Audio Easy, can be used to create a nonidentical copy to simulate double-tracking. The difference between the orange line (tuned) and gray line (original) shows the amount of pitch clashing that will be heard when the two are combined.
If you have the time and the tracks available, it's a good idea to record doubles of key parts. Parts that were recorded for the purpose of capturing the perfect take can often be appropriated for creative doubling. If you find yourself without the necessary extra tracks, don't despair; there are several techniques you can use to accomplish a similar effect, and each technique adds its own character.
Your Cheating Parts
When in doubt, cheat. If the chorus happens three times, take the second and third times, paste them alongside the first, pan them to opposite sides, and you've got three times as many background singers. (You can also use that technique with instrumental parts.) Then copy the complete ensemble to the location of the second and third choruses. When necessary, time-correction software such as Antares Vocalign can be used to match the different takes to an unnerving precision.
You can also get a lot of mileage out of a single track when dealing with verses and other nonrepetitive parts. Duplicating a part simply increases its volume, but delaying one copy a few milliseconds creates a nice sonic rub (see Fig. 1). Be sure to lower the volume of one part a significant amount and pan it to the side; otherwise, you'll wind up with an undesirable comb-filtering effect. Doubling and delaying is the basis of chorusing, but the delay time on a chorus is modulated, creating a livelier effect.
The copy-and-delay technique is also useful for accenting parts without increasing their volume. In Web Clip 1, I used it to make a triangle part dance across the ceiling. The track is slightly delayed, significantly lowered in volume, and panned far to one side. The sense of altitude is palpable.
Lowering the level of the copy allows the original to be the dominant sound, merely colored by the presence of the copy. Be careful with delay time and stereo separation. Up to a point, increasing the delay time increases the effect, but beyond that point, the copy starts to separate from the original. Increasing the stereo separation leaves a larger hole in the middle, which can be a good or a bad thing.
Pitch to Fit
Doubling a part adds depth to a sound because of the subtle clash of frequencies that results from differences in intonation. Combining a pitch-corrected part with the original replicates those subtle differences and the note-to-note variations in an authentic doubled part (see Web Clip 2).
If you don't have automatic pitch correction available, you can simulate it by detuning one copy by a few cents. Better still, detune one copy up and another down, pan them to opposite sides, and combine them with the original, positioned near the center. That is a classic synthesis technique for creating gentle (and warm) doubling or extreme dissonance, depending on the degree of detuning.
Up and Away
Pitch correction cannot convincingly transpose an exposed part by an octave, but when the part is used for doubling, artifacts resulting from the large pitch shift are less noticeable. They can even be advantageous.
Other effects, from EQ to compression, can be used to thicken a part. Distortion, re-amping, and waveshaping plug-ins are obvious choices for guitar parts, but they can also be used to great effect with other instruments or vocals. Keep in mind that no matter what method you use — including genuine double-tracking — the pan and level of the doubled parts have a profound effect on the results. Listen carefully and be willing to experiment.
Brian Smithers teaches audio workstations at Full Sail Real World Education and music technology at Stetson University. He is the author of SONAR 5 Ignite! (Thomson Course Technology, 2005).