gRainbow Is A Free Pitch-Detecting Granular Synthesizer

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Brady Boettcher releases gRainbow, a free pitch-detecting granular synthesizer plugin for Windows, macOS, and Linux.

Granular synthesis is a complex and fascinating area of audio research, and it’s not uncommon to see developers push the boundaries of what is possible with it, thanks to fresh perspectives and brilliant intuitions.

It’s within this scenario that Brady Boettcher, an independent audio developer, shares with the world his open-source, cross-platform synthesizer gRainbow, a cross-platform synthesizer that uses pitch detection to choose candidates for granular synthesis or sampling.

The main goal of this project was to overcome a few shortcomings of traditional granular synths, for example, the inharmonicity generated by pitch variations in the input clip and the unwanted artifacts which are the result of extreme time-stretching.

To overcome these problems, gRainbow uses longer, pitch-diverse audio clips. It automatically produces harmonics matched for MIDI input and avoids too much time-stretching by generating harmonics that are already near their target pitch.

It works like this: when an audio file is loaded into gRainbow, a pitch detection analysis is run to segment the clip into discrete pitches over time, and each one is assigned a color (hence the rainbow visual nature of the GUI).

Next, the synth finds up to 6 pitch-matched position candidates for each note, guaranteeing harmonically agreeable grains.

Candidates are a collection of viable positions in the audio clip where the pitch is harmonic with a particular note.

Finally, the user can customize each note and its generators (i.e., changing parameters and candidates) to their liking and can save all the processing into a preset for instant recall.

The GUI is organized with the 12 notes of the chromatic scale displayed at the bottom, a neat rainbow at the center displaying the harmonic profile of the audio analyzed, and some useful global controls on the sides.

You’ll find traditional controls over the grain’s envelope, like their shape and duration, a global ADSR amplitude envelope, and a multi-mode filter with Cutoff and Resonance parameters.

Furthermore, there are some other specific parameters to customize the granular synthesis process: the Pitch Adjust, Pan Adjust, and Position Adjust, paired with their respective Spray control, which can select a range of randomization.

gRainbow is available for Windows, macOS, and Linux in VST3, AU, and LV2 plugin formats. You can download the current version (v 0.2.2) via Github.

Download: gRainbow

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Fabio is a sound designer, sound engineer, and electronic music producer from Italy. His works can be found under the name HydraTek.

18 Comments

    • Doesn’t works as AU in Logic 10.5.1 and Ableton 11.
      Doesn’t works as vst in Ableton 11.
      Doesn’t work as stand alone on macos 10.14.6

      • Hi Ben, I just made a new release that fixed this issue! The standalone and AU should work for MacOS 10 now.

  1. Honestly, they could have just made a regular good granular synthesizer, the freeware plugin ecosystem is sorely lacking those.

    Buuuut after testing I have to say this is pretty cool in its own right, it’s a lovely little plugin.

  2. Why do open source/free plugins have to almost always be ugly? This is why most people don’t use free stuff in professional studios.

    • Because most free plugins are mostly focussed on functionality, they are usually made by programmers, not UI designers so they just don’t put as much effort, i don’t think they’re trying to target a demographic either and if they are it’s probably not studios.

    • Byron Penot

      on

      While I’m no fan of the GUI, it’s not in any way “ugly” enough to prevent me from using it if I like what I hear and if I can get on with the workflow.

      I have a handful of much less attractive free (and paid) VSTs in my plugin folder that I use on a consistent basis.

    • have you ever heard some kontakt libraries with default UI built in like Performance Samples.

      they do that cause they want to cut cost of production, and same aspects of VST Devs out there.

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