Pitch-shifting effects are widely available for audio software, but most don’t work well with voices. The reason is simple: the human voice contains various fixed frequencies due to the natural resonances of the vocal tract and the head – called formants. These stay the same even though we sing notes of different frequencies. So, although a basic pitch-shifting algorithm changes individual notes correctly, it changes these formant frequencies at the same time – and the result sounds unnatural. VoiceMachine allows you to change the formants of the voice independently from the pitch. There are two plug-ins provided with the VoiceMachine – the Processor and the Generator. The Mix control lets you balance the original and processed sound, and Balance affects the stereo balance of the processed sound. The Pitch control lets you transpose vocals by an octave in either direction in semitone steps, and Fine control lets you adjust the pitch within a semitone – without affecting the formant frequencies. Pitch invasion
The Formant parameter can be separately varied to change the formants without changing the pitch of the notes. This lets you make a female voice sound more masculine, or create chipmunk-like voices. Vibrato controls are provided, and vibrato tempo can be synchronized to a song tempo in a MIDI sequencer. You can also control the pitch of the processed sound by sending MIDI notes to the plug-in from your sequencer or MIDI keyboard. The Generator processes a single voice to produce four separate MIDI-controlled voices – each with independent formant, vibrato, level and balance settings. MIDI control can be used to create harmonies. Just create MIDI notes with the additional pitches you want to use, and let these control the four voices in the Generator. When I listened to the results, although the pitch-shifting worked well, there were clearly-audible warbling and glitching artefacts. Both plug-ins have nine presets. The Processor’s Harmonic Duet produced useable results with a female vocal, but the other presets are best described as “special effects”. The Generator’s presets all produced wacky sounds – again, great for special effects. I tried changing the formants on a female vocal without shifting the pitch. The effect worked well enough when blended with the original voice. However, the processed sound was muddy.


The VoiceMachine is ideal for anyone looking for special vocal effects, and can be useful for creating harmonies to use in song arrangements.

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