A polyphonic pitch-shifting plugin built using open source libraries.
Pitches are controlled by midi.
My goal is to create something similar to Antares Harmony Engine or the "Messina" device that Bon Iver uses to create vocal harmonies.
- The pitch of the input signal is estimated using the pitch detection module from the aubio library.
- Target pitches are identified based on which midi notes are active.
- For each target pitch:
- The input signal is duplicated and shifted to the target frequency.
- Pitch shifting is done using the phase vocoder implementation from the aubio library.
- The pitch-shifted signals are summed together and written to the output buffer
- fix all NaN issues
- figure out why it sounds better when I sing higher
- try lpf output signal
- improve pitch detection (lpf input signal?)
- experiment with different window sizes and overlap
- fix stereo routing
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voices do pitch shifting and add their own shifted signal to the frequency domain
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this way there is only one forward and one reverse pvoc operation
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PhaseVocoder: wrapper around aubio pvoc
- doForward: float[] -> cvec_t[][]
- doReverse: cvec_t[][] -> float[]
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HarmonizerAudioProcessor: holds a Synthesizer, does setup for Synthesizer (e.g. add voices), does forward AND reverse phase vocoder transform
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HarmonizerSynthesizerVoice: responsible for pitch shifting one note and adding that note to the shared cvec_t
- Needs a reference to HarmonizerAudioProcessor to get forward phase vocoder signal and current pitch
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HarmonizerSound: a simple description of a sound. Required by the Synthesizer class.