This innovative six‑band EQ plug‑in applies a little music theory to the humble equaliser.

Whether it’s authentic recreations of hardware classics, multiband dynamic or AI‑powered, our EQ options have come a long way since the humble treble and bass controls of days gone by. But Plugin Boutique’s Scaler EQ adds a new twist to the EQ knob: this is an EQ that, thanks to its awareness of the key/scale of the music you’re processing, can apply adjustments focused on just the notes/frequencies in (or out of, or both) your project’s key. It’s the kind of idea that, once you’ve heard about it, makes you wonder why it isn’t already a thing!

Lightbulb On

In brief, Scaler EQ is a six‑band EQ plug‑in that supports a full range of traditional EQ options: peak (parametric), low/high cut and low/high shelf, with both fixed and dynamic operation, stereo, Mid or Sides options, and external side‑chain support. There are also Magic Shelf (both high and low) options that offer additional tweaks for improved results with stereo signals. The plug‑in provides a comprehensive suite of controls in each case, so you could easily use Scaler EQ for any of your routine EQ duties. It also includes spatial width options and input/output controls with their own limiters for managing your levels.

But the really novel option is Harmonic Peak mode. The control set is identical to that of the peak mode filters but, as can be seen in the screenshot, a Harmonic Peak band consists of multiple individual filters positioned around the centre frequency of the band. The position of the individual filters is determined by the frequency of the notes that are in (or out) of the currently selected key/scale combination. The Detect Key option (located in the top toolbar) will automatically detect your project’s key, or you can specify it manually. The Scale Switcher buttons allow you to store up to three key/scale combinations, and you can use automation within your DAW to switch between these. As you do so, any Harmonic Peak bands will follow, adjusting the frequencies of those narrow individual filters to match the notes within the scale.

While you can change this behaviour, by default, when you boost with a Harmonic Peak band, the individual filters focus on notes within the chosen scale — and when you cut, the filters focus on notes outside the scale, so as to reduce any harmonic content that’s out of key. In addition, as for band four in the screenshot, there is a Harmonic Peak +/‑ mode — this combines these two behaviours in a single band. And, yes, the Harmonic Peak modes can also be dynamic.

Beyond The Concept

Even as a flexible conventional EQ plug‑in, Scaler EQ is capable and modestly priced, but it’s definitely the scale‑aware EQ’ing that makes it stand out from the crowd. There’s certainly an appealing logic to the underlying idea but I think the practical potential of this plug‑in is just as interesting as the concept. And having experimented with the plug‑in on a number of projects during the review period, I’m still not sure I’ve fully grasped its full potential, partly because it is a novel approach but also because it opens up some equally novel possibilities.

If applied to a percussive sound that has little obvious harmonic relationship to the project’s key/scale, a Harmonic Peak band can emphasise the ‘in key’ frequencies.

You can, of course, use it to sweeten up a vocal, individual instrument or a bus. In that context I found that a Harmonic Peak band could subtly tame those ‘out of key’ frequencies to deliver a little extra clarity, though you do have to use it with care — if applying too much gain, I could hear some artefacts creeping in. Scaler EQ also has strong potential as a sound design tool. For instance, if applied to a percussive sound that has little obvious harmonic relationship to the project’s key/scale, a Harmonic Peak band can emphasise the ‘in key’ frequencies, so that the percussive sound becomes ‘tuned’. I’m sure that, given more time, I could unlock more of its potential, so I’d absolutely encourage you to try the free trial version for a spin.