Soft Loop Audio has released Harmonic Echo, a free generative MIDI delay plugin for macOS, Windows, and Linux.
I was contacted by the developer behind Soft Loop Audio about this release, and instantly loved the concept. After spending some (very short, unfortunately) time with Harmonic Echo, I can safely say it’s unlike any MIDI effects I’ve tried before, and I’m looking forward to testing it further later this week.
Instead of behaving like a traditional delay (as its name might suggest) that simply repeats incoming notes, the plugin generates brand-new musical material using a mix of music theory and physics-inspired logic.
Harmonic Echo is essentially a generative MIDI effect that turns your note input into evolving melodic and harmonic patterns. You set a key and mode (major, minor, Lydian, and more), and every generated note stays locked to that scale.
That means you can experiment with melodies and harmonies without worrying about wrong notes creeping in. I’ll admit that this isn’t the best way to learn music theory, but it is definitely a nice option for jamming or quickly generating new ideas.
I had an absolute blast jamming with this last evening and loved how playable the plugin feels. The interface visually reminds me of video games like Guitar Hero, with cascading MIDI notes sliding across the screen. Actually, the whole experience feels similar to playing a game, except you’re making music instead of chasing a high score.
You can trigger echoes manually and audition ideas directly from the UI, but my favorite feature is the polymetric “Hold” engine. This groups echoes into rhythmic clusters that don’t always sit neatly on the grid, making it easy to stumble upon complex patterns you probably wouldn’t program manually in your DAW.
There’s also a handy button, so once you’ve found something inspiring, you can commit it to MIDI and take it further.
Unfortunately, I haven’t had the chance to push Harmonic Echo to its limits yet. It’s the end of the year, things are busy, and my testing time has been limited.
That said, I already know I’ll be revisiting this one properly in January. It’s going straight onto my list of the best unusual free plugins of 2025, too.
Harmonic Echo is available as a free VST3 plugin for macOS (10.15 or later), Windows 10+, and 64-bit Linux systems. It’s completely free and, according to the developer, always will be.
Download: Harmonic Echo
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Last Updated on December 30, 2025 by Tomislav Zlatic.
