Sky Blue EQ4 is a new FREE tone-shaping EQ plugin for macOS and Windows


Sky Blue EQ4 is a free and open-source EQ plugin by Aris Kiriki-Liszt. The Maag-like plugin pays homage to the EQ4M, Maag Audio’s successor to the original NTI EQ3.

With the original NTI EQ3 proving hard to find nowadays, the more powerful EQ4M is a fairly sought-after piece of hardware.

The significance of both hardware units is that the NTI EQ3 marked the introduction of the Air Band. At the same time, the EQ4M provides the same musical results with even more headroom, thanks to improved design and higher tolerance components.

Like the hardware EQ4M, the Sky Blue EQ4 offers five fixed-frequency bands: Sub, 40 Hz, 160 Hz, 650 Hz, and 2.5 kHz, followed by the Air Band. In this case, the Air Band is represented by the Sky High/Gain controls.

Maag Audio’s Air Band is a shelf boost, adjustable between 2.5/5/10/15/20/40 kHz. The Air Band is slightly unusual because the corner frequency far exceeds the audible range.

You’ll notice that there are now potentially two 2.5 kHz bands, but since the Air Band is boost-only, cutting with the other 2.5 kHz shelf brings some interesting results.

Sky Blue EQ4 functions much like the EQ4M in that it’s effortless to use, and the regular bands do what you’d expect, for the most part. The provided bands are ideal for tone-shaping and thickening the low-end rather than surgically removing any unwanted elements.

The plugin differs slightly by avoiding a somewhat unusual side effect of the hardware. When you boost any given frequency with the EQ4M, it can boost the entire spectrum, sometimes quite significantly.

While it’s not rare for analog gear to have quirks, the EQ4 plugin perhaps more accurately represents any adjustments you make without any widespread gain increase.

However, depending on how you run it, the plugin has some behavior variations, like EQ cramping, and it’s worth checking out the developer’s notes on GitHub.

Several developers have tacked the EQ4M, including Brainworx and Universal Audio.

It’s been a decent few weeks for EQ freebies, with the recent update of VOS BootEQ in the mix, too.

Sky Blue EQ4 is available in AU and VST3 formats for macOS and Windows.

Download: Sky Blue EQ4 (FREE)


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James is a musician and writer from Scotland. An avid synth fan, sound designer, and coffee drinker. Sometimes found wandering around Europe with an MPC in hand.


  1. Will try out this freebie. Sometimes the free stuff is as good or better than the paid plugs. I have the Maag EQ2 and 4. I like the Maag 4 better. The Maag 4 is good for adding low end and air to a track. But I may stick with adding a full-fledged EQ to my master tracks. I’m just learning how to appreciate those fixed frequency EQ’s. I’m finding that on that non-muddy stuff I can get the sounds I want faster. That PSP Noble Q works excellent on clean sounds.

  2. Beautiful GUI, just like the hardware. Personally I have had great results with Luftikus by Ikjb Plugins, so I will pass on this. Much thanks to the Developer for creating a 2nd Free Maag EQ4 emulation.

  3. I installed Sky Blue 4 eq. It shows up and works fine on Cakewalk Bandlab but not on Pro Tools. I have relaunched Pro Tools and still does not show up. Any ideas?

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