VOCALOID

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VOCALOID

Developer	Yamaha Corporation
Initial Release	January 15, 2004
License	Proprietary
Language	C++
Website	https://www.vocaloid.com/en/

VOCALOID (ボーカロイド, Bōkaroido) is a speech and singing synthesis software developed by Yamaha Corporation, first released in 2004, that utilizes concatenative synthesis to generate artificial vocal performances. Unlike formant-based synthesis, which models the acoustic properties of the vocal tract, VOCALOID constructs vocals by assembling pre-recorded phonetic fragments—termed phoneme libraries—from human voice providers. Each library contains thousands of samples, captured at multiple pitches and dynamics, which the software aligns and blends algorithmically based on user-input MIDI data and vocal parameters (e.g., vibrato, breathiness, and articulation).

The synthesis engine operates via a parameter-driven interface, allowing users to refine timing, pitch transitions, and expression through controls such as Velocity, Note Duration, and Dynamics. Advanced versions, including VOCALOID4, introduced spectral blending techniques to reduce mechanical artifacts between phonemes and added features like cross-synthesis for hybrid voice creation and VocaloWander for nuanced pitch modulation.

The software's architecture prioritizes customizability, enabling developers to create third-party voicebanks using proprietary Voice Library Maker tools. These voicebanks adhere to strict phonetic labeling protocols and require extensive recording sessions to cover linguistic nuances, including vowel-consonant transitions and prosody. VOCALOID has also integrated real-time rendering in recent iterations, allowing dynamic pitch and expression adjustments during playback.

Yamaha's technical documentation emphasizes Vocaloid’s reliance on F0 contour manipulation (fundamental frequency) and spectral envelope interpolation to achieve naturalistic vocal timbres, though limitations persist in replicating human-like emotional expression and spontaneous vocal fry.