Tilr TetraOP is a free wavetable FM Synthesizer plugin for macOS and Windows, released as part of the KVR Developer Challenge 2026.
TiagoLr, or Tilr, is a developer of free, open-source plugins that have garnered considerable popularity. His latest synth will soon be released as a commercial product by reFX.
This year’s KVR Developer Challenge (2026) has just started, and Tiago is participating. Tilr has developed TetraOP for this occasion.
Tilr TetraOP
TetraOP is a new, powerful, free, open-source Synthesizer for macOS, Linux, and Windows. TetraOP is Tilr’s third Synthesizer after the Rippler X and Rippler.
It uses the same design language and incorporates many elements familiar from the Rippler X alpha version. At its core is a combination of wavetable and FM synthesis.
Exciting is the oscillator architecture. Four oscillators that can either act as a classic wavetable oscillator block or as four operators, forming the TetraOP into a modern FM synth. They support up to 16 Unison voices per operator with five available unison modes.
Each wavetable oscillator offers classic features familiar from other synths, including level, fine-tune, phase, as well as various wavetable modifiers. You can find bend, skew, formant, and more. They ship with factory wavetables, but you can also import new ones.
Things get even wilder when you delve into the FM side of the oscillators. On the bottom right, you can find an FM and RM routing matrix with 10 pre-defined layouts. Alternatively, you can create your own algorithm/layout for either FM or RM routing.
Each oscillator/operator also has an option to modulate itself. That’s not all. There are also eight phase distortion modes, giving you Casio CZ-style sounds. From here, it goes into a dual multimode filter.
Filter & Modulation
Whether an oscillator is routed in the filter can be selected within the respective filter. This also allows you to easily bypass it and custom routings.
Each filter offers five types with four modes each, including digital, analog, 303, phase, and more. They are tweakable with classic controls, and a built-in drive adds extra spice.
Tilr has also incorporated a fair amount of modulation into the TetraOP. There are four ADSR envelopes, four function generators that also act as LFOs, and a random generator. Plus, there are four macros, velocity, aftertouch, and mod-wheel.
Drag-and-drop support lets you easily assign modulators to parameters. They are then displayed in a modulation matrix with additional options on a separate UI page.
A click away on the second UI page of the new Tilr TetraOP is a multi-FX engine perfect for refining your sounds or giving them the final touch. Eight different effects are available, and you can reorder them with drag-and-drop as well.
You can work with a compressor, a multimode distortion, a chorus, a phaser, a delay, a reverb, and an EQ. Each of these effects comes with various parameters, making them fully tweakable. Better, the parameters are also modulatable.
TetraOP ships with a small amount of factory presets. I’m pretty sure more sounds will come during the KVR Audio Developer Challenge 2026.
First Impression
We may no longer have a Rippler synth as a free download, but Tilr has now gifted us with an exciting wavetable and FM Synthesizer. The feature set is rich and offers many sound design options.
Commercial synths might offer a bit more, like a wavetable editor or more oscillator modifiers, but for a free synth, this is already at a high level. Bringing wavetable and classic FM synth fans together in one instrument is neat.
So you have the best of both worlds plus an open door for hybrids. This release is definitely a highlight of this year’s challenge. Thanks Tilr!
Tilr TetraOP is now available for free download as part of the KVR Developer Challenge 2026. It runs as a VST3 and AU plugin on macOS (native Apple Silicon + Intel), Linux, and Windows.
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