About Hatsune Miku

Hatsune Miku (初音ミク) is a singing synthesizer application and its female character, developed by Crypton Future Media. It uses Yamaha Corporation's Vocaloid synthesizing technology. Her voice is sampled from Japanese seiyuu (voice actress) Saki Fujita.

Crypton released the first of their "Character Vocal Series", Hatsune Miku, on August 31, 2007.
On April 30, 2010, an updated version of Miku called Hatsune Miku Append was released containing a package of six different tones of Miku's voice:

• Soft (gentle, delicate voice)
• Sweet (young, chibi voice)
• Dark (mature, heartbroken-like voice)
• Vivid (bright, cheerful voice)
• Solid (loud, clear voice)
• Light (innocent, heavenly voice)

This was the first time a Vocaloid has such a release and more Append are reported from Crypton Future Media at later dates.

Hatsune Miku Dark Append - Hirari, Hirari

Source: Wikipedia