Even though it’s been around for a long time, parallel processing has become a hot topic in music production in the last few years, and for a good reason; this way of processing audio has many benefits, including performance optimization, consistency, and flexibility. The core idea behind parallel processing is that when we use it on a sound the sound gets split in two or more layers that include the dry sound plus one or more wet variants of it that become additional elements in the mix. This additive quality is what makes it so attractive in the mixing stage, because it bolsters bigger, richer and fuller mixes through the conjunction and blending of several strains of each element, adding a lot of complexity and depth to otherwise weak and dull mixes.
This is probably the first parallel effect you used before you even heard about parallel processing. Time based effects like reverb and delay are the most common and widely spread effects used in parallel, and can be found in numerous applications like DAW templates, samplers, synths and drum machines. Apart from the usual application, a reverb set in parallel with short decay time and size values, can be used to add an additional layer of energy to a sound, making it bigger, warmer and deeper. It’s very important to place a high-pass filter before the reverb though, in order to avoid low-end frequencies from being affected. A gate noise or a transient designer placed after the reverb can also be useful to control the reverb tails.
Delay is well known for its ability to add depth and dimension to a mix by recreating a virtual space based on sound reflections, but it is not so well known for its potential to fatten up sounds. With several delay units set in parallel, as well as low time and feedback values, you can dial in additional layers of reflection conglomerates to create massive walls of sound or simply add more texture and grittiness to any sound source. Use a diverse array of time settings across the different delay units, including out of sync time values, for more extreme results.
Parallel compression is another popular and widespread type of parallel effect.This technique originated from the desire to balance the dynamic range of uncompressed signals with the controlled and tight character of compression. When compression is set as an insert, the original signal gets transformed, losing part of its dynamic range and having its options reduced to just one: the amount of compression applied to the dry signal. When we use compression as a parallel effect, that is, as a send effect, we can layer the dry and the wet signals together in the desired proportion, having the best of both worlds.
Another common effect used to add warmth and excitement to a mix is parallel distortion. This effect can be used on any type of sound, but it’s best to place it after an EQ with low and high pass filters, so that we can choose the parts of the frequency spectrum that get affected by it. With this setup, you can add some extra harmonics to the desired frequency of any sound source.
Similar to parallel compression, parallel limiting can add some real punch to a sound with a more precise control over the peak levels and a more straightforward setup. All you have to do is to adjust the ceiling and the gain levels and then send the desired amount of dry signal into the return track where the limiter is located. You can limit the signal at any level you like and then blend it in with the original sound in order to give it a very controlled overall boost.
This effect is great to add more attack and/or sustain to any sound, and its effect is increased when used in parallel. As opposed to most of the other effects in this list, transient designers are capable of adding more punch and weight to specific temporal zones of the sound like attack and sustain, which is great to make all the elements in the mix interlock perfectly in terms of dynamics and intensity. To setup this effect, all you have to do is to adjust the desired attack and sustain levels and then send the desired amount of dry signal to the return track.
Similarly to distortion, frequency shifting can yield some incredible results through the addition of extra harmonics into the original sound. By shifting the frequency content of the sound, we can get a duplicate layer that even though it sounds fairly close to the source, it contains a different harmonic structure. This introduces new harmonics into the composite sound that we get through the sum of the two signals, giving rise to fuller and more richfull sounds.
It may sound strange to use EQ in parallel, but it can be very useful to boost certain frequencies with more intensity than with a regular EQ insert. Another interesting possibility that opens up with this technique is the option to set up multiple EQs in parallel and alternate between them throughout the song, something that isn’t possible with inserts. It also allows you to set up multiple EQs with very different settings and compare the results between all of them in a non destructive way. As with all the rest of parallel effects, it’s useful to set up an initial EQ to being able to filter out low and high frequencies before the signal hits the boosting EQ to avoid duplication of unwanted frequencies.
In this article we’ve learned about this advanced and popular production technique called parallel processing. More specifically, we’ve learned about some benefits it provides such as performance optimization, consistency, and flexibility, as well as some concrete examples of parallel processing used with popular effects such as reverb, delay, compression, distortion, limiting, transient design, frequency shifting and EQ.