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Sound Design in RX 7: Sonic Variation with Creative Selections

by Toby Pitman, iZotope Contributor April 22, 2020
RX 7 spectrogram after some sound design
Getting creative with selection tools in RX 7

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This is Part 3 of a four-part series written by Toby Pitman, sound designer for Netflix's Dracula. Read Part 1 here, Part 2 here, and Part 4 here.

RX 7 is jam-packed with powerful selection tools that you can leverage to create some interesting sonic variation from a single sound source. These techniques can be used in music production, game audio, and score production for film and TV. The key is simple: experimentation. 

In this article, we’ll discuss how these RX 7 selection tools can help create interesting sonic variations from a single sample.

Getting to know our audio

For this example, I made a four-bar loop from an analog modular patch.

Spectrogram view of our original synth audio
Spectrogram view of our original synth audio

Synth Example

Frequency band selections

This idea is similar to using a Moog 914 Fixed Filter Bank, which is a series of fixed bandpass filters. We can mimic this using the Horizontal Selection Tool (F). While the 914’s frequencies are fixed, RX 7 allows you to not only choose your own frequency bands and their bandwidth, but also the number of bands.

Let’s start with some narrow horizontal selections. When making your selection, you can change it up anytime by Adding (holding Shift) and Subtracting (holding Option or Alt). You can widen the bands by hovering over the edge of the selection to reveal the selection handles. This is useful for fine-tuning the frequencies you want. Here’s my selection:

Selected audio bands in RX 7 Spectrogram
My selected audio bands

You can hear your selection using the Play Frequency Selection option in the transport. To export your selection, you have a couple of choices. You can export it to an audio file using File > Export Selection, where you can choose the file format, bit depth, etc. and save to disk. The other option is to Copy the selection and choose File > New From Clipboard to Paste it to a new RX document. This can be useful for extracting and reprocessing a selection before pasting it back in.

Here’s my exported selection:

Band Selection

You can hear that I’ve made narrow band selections that are harmonically related, yielding a pleasant, ambient-sounding variation of my loop that's perfect for a breakdown section. You’ll be surprised at how many interesting variations you can pull from content like this.

Chord-based selections using the piano roll

You should also be aware that the RX interface has a piano roll, which you can activate with a right-click on the Frequency Scale. This allows you to zero in on note selections. Here I’ve made a selection with just the notes of C minor, extracting an almost static drone from all the chords in the sequence.

Again, you can achieve tons of interesting results using the piano roll for selections. It’s similar to the effect of vocoding, but you’re not imprinting anything else onto the sound.

Selecting bands related to a C minor chord using the spectrogram's piano roll
All the bands in this example are related to a C minor chord.

C minor selections

Creating complex variations from a single source

Another cool technique is to cherry-pick note selections from chords—with or without harmonics—and combine different high- and low-frequency information to create different tonal combinations from the original source. I normally paste these note selections into a new document using File > New From Clipboard, then save or export them as previously discussed for further editing and arranging in my DAW.

Some note selections pasted to a new RX document
Some note selections pasted to a new RX document

Trying to achieve these types of variations via programming or conventional filtering would take forever. In RX 7, however, you can produce a large amount of varying content in a fraction of the time that traditional techniques would require. Here’s a quick montage of some variations edited together to give you an idea—you can also try this on individual elements in your mix to create some ear candy on repeated sections:

Variation

Getting random

On the flip side of all this musical stuff, you can also use random selections that aren’t harmonically related. Each note includes a series of overtones. When you select random harmonics from two or three different pitches, they can crash into each other and produce clangorous variations—similar to ring modulation—that are also great for sound design work. Here’s the same synth loop with some heavy use of random selections, Variable Pitch and Time, and some pasting techniques—Paste Special > Mix—to mash selections back over each other. What I end up with is some sort of weird sci-fi/horror texture.

Morph

Proof that RX 7 is just as good at breaking sound as it is at restoring it!

Conclusion

Hopefully, these examples have given you some ideas for some sonic experimentation in RX 7. This kind of frequency extraction technique has a very distinctive sound to it and can yield some interesting results, depending on what you use to process it. You can see that it’s possible to get a lot of mileage from a single audio file—the key is simply to experiment and have fun with it!

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