The Character Vocal Series (キャラクター・ボーカル・シリーズ) (abbreviated CV; CVシリーズ) consists of Crypton Future Media, Inc.'s most famous set of vocals. These vocals are all the result of voice acting.
The Character Vocals were the successor to the initial unnamed VOCALOID "series" which consisted of MEIKO and KAITO, both of which were sold by Crypton Future Media, but developed by YAMAHA. The intention of the Character Vocal series during the VOCALOID2 era was to become the "standard" vocals for the VOCALOID2 engine and would act as replacements for MEIKO and KAITO. This intention was dropped when Bplats and Yamaha released the VY series.
The CV series was the first set of VOCALOID voices developed by Crypton Future Media. Hatsune Miku was officially the first Crypton Future Media VOCALOID.
The concept of Character Vocals was to produce a specific vocal quality, rather than to be professional vocalists like other VOCALOID voices. The VOCALOID vocals were often noted for thick and ugly results, so when making Hatsune Miku, MEIKO was used as a baseline for what the series would achieve. Wat wanted far more attractive vocals from Miku than what had been previously provided, with more flexible results in terms of age and gender. Ideas formulated from Miku were implemented into the rest of the series, with each vocal having varying qualities.
Their voice goals were based on how sound travels, hence the use of "音" meaning "sound" in the names of the products. It was difficult to find professional vocalists who would lend their vocals for the VOCALOID™ software. Therefore, the direction of the Character Vocal series was to be a more characteristic set of vocals. KAITO and MEIKO were created to generalized vocals. By using voice actors for the Character Vocal series, Crypton could give particular sounding vocals.  Still, despite this, the initial target audience were professional musicians.
Initially, only 3 products were designed for theVOCALOID2 engine, "CV01" (Hatsune Miku: based on sound when it first begins traveling), "CV02" (Kagamine Rin & Len: based on mirrored or reflected sound), "CV03" (Megurine Luka: based on sound after it has traveled), all of which are voiced by female vocalists.
Due to the series' success, additional vocals called "Appends" were added for each character, starting with Hatsune Miku Append. The Appends were an attempt to give the Character Vocals a "rainbow of colors" and were designed to be expressive vocals, expanding the overall usefulness of each individual vocal. This lead other studios to begin producing their own expressive vocal packs, such as Megpoid Extend. This expansion also lead to the updates of MEIKO and KAITO. In VOCALOID3 they were stated to also recieve "Appends," though it was noted the direction of their Appends were different compared to the CV series. Megurine Luka is the only member of the CV series that does not have an append package.
Due to the interest in selling their voice products to a broader audience and expanding the languages producers could use, all vocals made by Crypton Future Media were assigned English vocals during the VOCALOID3 era (excluding Rin & Len, who received their English vocals in their VOCALOID4 release. They, as well as Luka, had no V3 release). These upgrades included the Character Vocal series, which already had one member (Megurine Luka) with English capabilities. Hatsune Miku was once again the first product to have her English vocal worked upon.
However, the overall success of the Character Vocal series lead to a missing direction for the VOCALOID™ software, with much of the cause resting on the Hatsune Miku vocal. In fact, many VOCALOID™ issues and concerns are a direct result of the series' success. However, culturally the series had great impact on the VOCALOID™ software. In turn, other Vocaloid voices have been influenced by the series. Many other VOCALOIDs follow the use of the voice acted style of VOCALOID production, for example, Aoki Lapis.
Departure from VocaloidEdit
Over time the term "Character Vocal series" was used less by Crypton Future Media. Preferring to not use the term, they had also adopted the KAITO and MEIKO vocals from VOCALOID3 onward. Currently, they are collectively known as "Piapro Characters". On August 31st, 2019, Crypton announced the end of releases on VOCALOID and the move to Piapro Studio, marking the departure of this series from VOCALOID.
- ↑ IT Media クリプトン・フューチャー・メディアに聞く（2）：「初音ミク」ができるまで (Interview with Crypton Future Media (2): How Hatsune Miku Was Born) February 22, 2008
- ↑ http://blog.crypton.co.jp/mp/2009/01/post-95.html [dead link]
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- ↑ https://blog.crypton.co.jp/l/2019/08/n1908311/
- ↑ https://twitter.com/labopton/status/1167698329389551616?s=19