SF-A2 was released the same day as Kaai Yuki and Hiyama Kiyoteru as a part of an "artist edition series". SF-A2 miki's direction was very different from Kaai Yuki and Hiyama Kiyoteru. Much of her planning and development was handled by HEARTFAST and the overall planning of the first three AH-Software Co. Ltd. vocals began in 2007. She was originally meant to be the partner vocal of Utatane Piko and was made with a different company, but due to problems, she was separated from her "brother" vocal.
She is voiced by Miki Furukawa (former bassist of the band Supercar; now a solo singer) and illustrated by Yuusuke Kozaki. Her creation was a joint effort by both AH-Software and Yamaha.
Also another demo song was given out on her official page.
SF-A2 miki follows a different intention to that of Kaai Yuki and Hiyama Kiyoteru; istead, she was created to have a wide range and to sound greatly different in her higher and lower ranges. She is a realistic CV VOCALOID based on her provider Miki Furukawa and faithfully captures her provider's vocal.
Vocal traits as noted:
She is regarded as one of the more "faithful" vocals, sounding more like her provider than many other VOCALOIDs.
Adjusting "PIT" or "BRI" can result in a more natural vocal.
SF-A2 miki often divides opinions. Some users say her voice is smooth and can be emotional while others dispute that claim, saying that while she sings well, she is not easy to use due to a combination of her pitching issues, the unwanted background noise, and firmness of her voice.
She has one of the largest optimum vocal ranges for VOCALOID2.
She and Nekomura Iroha joint hold the title of the second lowest optimum vocal range achievable by a female VOCALOID in the VOCALOID2 engine, Lily being the top one. The difference between her and Iroha is that Iroha is voiced by a male vocalist whereas SF-A2 miki is voiced by a female vocalist.
Her treble and bass have very different sounds to them with her treble range being much firmer sounding. The difference between her high and low ranges means she does not maintain the same stable tone if drifting up and down the octaves. Due to this, it is difficult to control her pitch without further editing or pitch correction software. Without this, she can have too much tense in her voice.
The versatile nature of the vocal means that SF-A2 miki is able to produce enough distinction in her vocal via adjustments to fill all 16 tracks of the VOCALOID2 editor.
At the time she was the most versatile Japanese Vocaloid and the only one who could manage to do this, fully replaced Hatsune Miku who previously had been the most versatile voicebank.
Very few VOCALOID2 vocals could create enough distinction within their results without a large loss of quality in the process. This lack of tone capabilities is exampled by releases such as Megpoid.
She has a habit of sounding too tense in the upper registries.
SF-A2 miki has the same tempo and range as fellow AH-Software vocal Nekomura Iroha. This makes her both a good alternative to Iroha, as well as a suitable partner due to being able to cover the same genre of music.
Phonetic notes as noted:
Because of an alleged pronunciation issue, she is often said to not be easy for beginners to use.
If a note set that includes a "-" filler phoneme is too short, she will skip the "-" phoneme entirely.
Software issues as noted:
Overall, the vocal fails to fall into the High Quality range and is considered at best among the Mid Quality vocal range. However, at the time of release in 2009, she was among the better releases VOCALOID2 had to offer.