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A virtual analog synthesizer inspired by the classic Roland Juno polysynths. By analyzing hardware measurements, firmware, and factory schematics, we are constantly pushing closer to circuit-accurate perfection. It's an ongoing journey, but we won't stop believin' that because it's free and open-source, we can get there together.
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Ultramaster Group was born in the year 2000, in a loft in Brooklyn, NY. Our bold mission: professional-grade audio software for the Linux ecosystem. We were young, idealistic, and perhaps a little bit ahead of our time.
Life eventually pulled us into different orbits. Karl went on to found the art and design powerhouse Kayrock Screenprinting, while Dave joined the engineering teams at Google. But the music never truly stopped.
Twenty-five years ago, we were targeting the Pentium Pro, working without the luxury of oscilloscopes, service manuals, or community hubs like ModWiggler and Reddit. Today, after decades spent designing Kayrock Powertools and scaling global infrastructure, we’ve returned to the Juno source code.
A lot has changed since the late 90s. Hardware is exponentially faster and DSP methodology has evolved. We have spent time heavily recalibrating and refining the engine for the modern era. While the interface remains intentionally familiar, the internal architecture has been overhauled for better performance and precision.
We are rereleasing KR-106 as an open-source project under the GPL to give back to the community that inspired us from the start. Our goal is to make this as accurate as humanly possible, and we would love for you to help us get there.
Ultramaster KR-106 is, and always will be, 100% free and open source. We don't take donations, but if you'd like to support the hands behind the code: for Karl, visit Kayrock Screenprinting or check out Kayrock Powertools. For Dave, just go use Google Maps or something.
Help us calibrate the KR-106 by recording a few factory presets on your hardware. We provide MIDI files that program your synth via SysEx and play test notes. Just hit play, record the output, and send it our way. The more units we hear from, the better we can model the real thing.