VOCALOID is a singing synthesizer application developed by the Yamaha Corporation. Song writers can generate authentic-sounding singing on their PCs by simply typing in the lyrics and music notes of their compositions. The software synthesizes the sound from “vocal libraries” of recordings of actual singers, retaining the vocal qualities of the original singing voices to reproduce real-sounding vocals. VOCALOID software is bundled with VOCALOID libraries from soundware companies under licence from Yamaha. Currently, VOCALOID can generate singing in Japanese and English.
According to Yamaha, VOCALOID itself consists of a score editor, which does the scale, song-word, and expression processing; the Vocal Sound Generator, the engine that synthesizes the vocals; and libraries (each comprised of a pronunciation database and a timbre database) for each vocal. New vocal libraries can be created by recording real voices pronouncing basic vocabulary and reproducing variation effects (such as vibrato) according to templates.
To synthesize vocal parts, the system retrieves data consisting of voice snippets, applies pitch conversion, and splices and shapes them to form the words of a song as input by the user. As this processing is done at the frequency-domain level, pitch can be easily changed according to the specified melody, and the voice snippets can be spliced in a way that reproduces smooth-flowing words.