“Parallel Processing” is a term that can describe a number of techniques engineers use in pursuit of punchy, relentless backbeats, rock-solid bass-lines, and vocals that speak with power and nuance.
At its most basic level, this family of tactics is at play whenever we duplicate an audio feed, and treat each copy of that feed differently.
Properly executed, parallel compression on a drum bus can help us achieve a consistent minimum audio level while retaining some organic dynamic range, and allows us to obtain powerful, up-front sounds that still maintain clear and natural transients.
But the game doesn’t end there: For decades, bold engineers have turned to a variety of parallel effects wherever they need to sculpt new tones that merge the best features of two or more sounds. Compression, limiting, distortion, even parallel EQ can be used on a wide array of instruments to great effect.
HOW DO I DO IT?
In a broad sense, the way we route to a basic reverb is a form of parallel processing: Our audio signal is effectively split in two, with some of the sound running through the sonic spin cycle before it’s blended back into the mix underneath our unadulterated “dry” sound.
In essence, we apply dramatic effects to a duplicate of a sound. Unlike reverbs or delays, which are traditionally fed to effect boxes through an aux send, tracks earmarked for other types of parallel processing are most commonly routed via bus assigns, patchbay “mults”, or simply duplicated within a DAW.
However you chose to route and duplicate your sounds, the concept behind all parallel effects is basically the same: fearlessly crush, smash, carve, distort, or sculpt your duplicate. Then, fold this hot twisted nugget of audio back into the mix alongside your original sound.
DRUMS AND DRUM BUS
For the iconic sound of “New York-style” compression on drums, get a good blend of drums together for your main mix. Then, simply route all your drums through another bus, squeeze to taste, and fold them back into the main mix alongside your clean tracks.
The goal here is to make sure your parallel drum mix is compressed to the point where it has precious little dynamic range. For this technique, a very fast attack time often works best – Don’t be afraid to chop off some of the transients and create a big, consistently thumping backbeat. Fast releases time that pump and breathe with the rhythm of the music are fair game, as are longer release times that create a smooth and consistent decay.
Depending on your tastes, the compressed drums may sound a bit dramatic by themselves, but that’s okay. When added to your original mix, this parallel bus acts as a supporting element, allowing you to bring up the beef and average level of your drums while preserving the original transients and much of the larger dynamic changes.
A similar approach can be applied to individual drums. Snare tracks are an especially common recipient of the parallel treatment. To bring more attack and consistency out of a snare drum or its corresponding reverb send, it can be fun to crush, EQ, and perhaps gate the original sound in parallel. Feel free to go for an unusual, even unnatural drum-machine sound, to add impact and excitement to your clean snare.
But be careful, and make sure to maintain perspective! These techniques can be a quick path to big, punchy and relentless drums. While it’s easy to get drawn into the addictive process of creating ever more exciting sounds, some productions will benefit from a significantly more understated approach.
As with drums, many of today’s engineers feel compelled to create distinctive and ever-present vocal sounds.
But this isn’t a contemporary phenomenon. Back in the 1960s, Motown engineers Mike McClean and Lawrence Horn were using a technique on vocals that they called “Exciting Compression”…