https://github.com/jurihock/robotone

MIDI-controlled polyphonic vocal harmonizer
https://github.com/jurihock/robotone

au audio audio-effects audio-plugins dafx dsp effects fourier harmonization juce juce-plugins lv2 pitch-shifter pitch-shifting plugin sdft sliding-dft stft voice vst

Last synced: 3 months ago
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MIDI-controlled polyphonic vocal harmonizer

• Host: GitHub
• URL: https://github.com/jurihock/robotone
• Owner: jurihock
• License: gpl-3.0
• Created: 2025-05-25T20:12:44.000Z (4 months ago)
• Default Branch: main
• Last Pushed: 2025-06-16T17:32:19.000Z (4 months ago)
• Last Synced: 2025-06-16T17:37:48.584Z (4 months ago)
• Topics: au, audio, audio-effects, audio-plugins, dafx, dsp, effects, fourier, harmonization, juce, juce-plugins, lv2, pitch-shifter, pitch-shifting, plugin, sdft, sliding-dft, stft, voice, vst
• Language: C++
• Homepage:
• Size: 97.7 KB
• Stars: 7
• Watchers: 0
• Forks: 0
• Open Issues: 6
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

          
# Robotone

![language](https://img.shields.io/badge/plugin-AU%20LV2%20VST3-blue)

![license](https://img.shields.io/github/license/jurihock/robotone?color=blue)

![build](https://img.shields.io/github/actions/workflow/status/jurihock/robotone/build.yml?branch=main&label=build)

![tag](https://img.shields.io/github/v/tag/jurihock/robotone?color=gold)

The experimental *Robotone* audio effect plugin applies a fixed pitch onto a sound controlled by a [MIDI](https://newt.phys.unsw.edu.au/jw/notes.html) note event. Originally this technique puts zero phase values on every [STFT](https://en.wikipedia.org/wiki/Short-time_Fourier_transform) frame before reconstruction [[1](#1),[2](#2),[3](#3)]. However, the phase zeroing effect is emulated in *Robotone* using the [Sliding DFT](https://www.dsprelated.com/showarticle/1396.php) as implemented in [SDFT](https://github.com/jurihock/sdft). This enables polyphonic usage in a single processing step.

The basic idea behind this effect is to reinterpret the frequency axis by replacing the DFT bin frequencies with overtone series as played on a MIDI keyboard. When applied to the vocal input, this particular modification produces a robotic sound at a fixed pitch. Additional phase vocoder based corrections result in pitch shifting. Unfortunately, the pitch shifted output does not preserve the formants. This issue might be resolved in a future version.

However both effect variants can be used to add a harmonic touch to vocals in a musical way. I suppose so at least...

## References

1. Vincent Verfaille, Daniel Arfib (2001). Adaptive Digital Audio Effects. https://dafx.de/paper-archive/2001/papers/verfaille_a.pdf

2. Vincent Verfaille, Udo Zölzer, Daniel Arfib (2006). Adaptive Digital Audio Effects. https://hal.science/hal-00095922/document

3. Udo Zölzer (2011). Digital Audio Effects. https://www.dafx.de/DAFX_Book_Page_2nd_edition/index.html

## License

*Robotone* is licensed under the terms of the GPL license.

For details please refer to the accompanying [LICENSE](LICENSE) file distributed with *Robotone*.