The truly virtual singer

Hatsune Miku is a well-known singer in Japan. But she is a cartoon and her voice was made by researchers in Barcelona...

In the UK we have one cartoon band - Gorillaz - but the Japanese are more used to pop stars who happen to be animations. Hatsune Miku is different: her singing voice is generated by a computer program sold by Yamaha. You can make her sing anything you like... which might explain why her biggest hit is a Swedish folk song in which she waves a leek!

A singing voice, just like a speaking voice, has a very complex sound. You've probably heard automatic speech on the phone, or on busses and trains, and you might have noticed it can sometimes sound rather unnatural. Synthetic singing is even more difficult to create, since it needs to have the right melody as well as sound like a voice. But researchers in Barcelona (at the University Pompeu Fabra) applied similar techniques as used for speech synthesis, and developed computer software that can sing any words you like, with any melody.

This "singing voice synthesis" was taken up by the music technology company Yamaha. Cleverly, they sold it not just as a piece of software, but as a set of vocal "characters" you can buy, each with their own visual appearance. Yamaha sell a variety of these characters, but Hatsune Miku is by far the most popular - all starting from when was a viral video hit with the Swedish folk song Ieven Polkka in 2006.

To record a Vocaloid vocal track, you simply need a file with the lyrics, and a melody in MIDI format. The system has a database of tiny fragments of recorded voice which it connects together, and also tweaks the sound so that the pitch varies smoothly in the right musical way. People who use Vocaloid to make Hatsune Miku sing might not realise it, but they're actually manipulating the voice of a vocal actor called Saki Fujita, who recorded all the voice samples.

When a Japanese Vocaloid user uploaded a video of Hatsune Miku singing the folk song and waving a leek (for no apparent reason) it was a big hit online in Japan. This made Hatsune Miku so popular that she even performed live in concert - quite an achievement for a fictional character! She appeared live onstage in front of hundreds of fans, through an optical trick based on the Pepper's Ghost illusion.

The live appearance wasn't even the highest point of her fame. After a petition by her fans, an engraving of Hatsune Miku was even included on board a Japanese spacecraft called Akatsuki that was launched into space in May 2010.