CARP Audio is offering Octapus, its octave effect plugin, for free for a limited time.

The offer expires in 48 hours, and the exact expiry time depends on your timezone, so download it as soon as possible if you want to grab it for free. It normally retails at €29.95.

Octapus is an octaver with a few features that go beyond what a basic octave plugin offers. It has two parallel time-stretching channels, one pitched an octave down and one pitched an octave up, each with its own volume slider for mixing into the dry signal.

Each channel also has a filter knob that works as either a low-pass or a high-pass, depending on which direction you turn it, which is useful for keeping the lower octave from cluttering up the low end of a mix.

The Detune function is where things get fun, though. It detunes the left and right voices of each pitched channel by a small amount. This lets you create a wider sound, similar to the voice detuning on a synthesizer. The effect works great on guitars and vocals.

CARP Audio also built this to preserve mono compatibility when used alongside the Spread function.

Spread uses the Haas Effect to push the pitched channels across the stereo field, adding width to the octave layers without affecting the dry signal.

There’s also an Audition Mode, which is essentially a preview button that temporarily sets the mix to 100% wet so you can hear exactly what you’re adding before blending it with the dry signal.

I found the interface a bit confusing at first glance, but it’s actually straightforward once you start using it. It didn’t take long to figure out what each slider and knob was doing.

As for sound, it works well on guitars as you’d expect, but it’s also worth trying on vocals and synth leads. If you need an octave plugin that goes a bit further than just pitch-shifting up or down, this one is worth a look.

Octapus v1.2.2 is available in VST3 and AU formats for macOS 10.15 and higher, and VST3 for Windows. Until a license key is entered, the plugin runs in Demo Mode, which is fully functional but adds occasional noise bursts.

Download: Octapus by CARP Audio (FREE for a limited time)

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Last Updated on February 27, 2026 by Tomislav Zlatic.