Miku might seem like nothing more than a high-pitched singing cartoon, but she's the spearhead and symbol of a radical cultural phenomenon. Her anime-inspired avatar was invented to sell Yamaha's Vocaloid 2 voice synthesiser program, launched by Crypton Future Media (CFM) in 2007, which lets anyone construct a song from individual phonic units stored in a database. You type the words into the program along with their mood, pitch and length. "Anybody can be a producer of Hatsune Miku," explains CFM's marketing director Kanae Muraki.

Miku's not the only Vocaloid character, but she's by far the most popular - her biggest hit, World Is Mine, has 15.6 million hits on YouTube. It's just one of an estimated 600,000 Miku works online, created by thousands of people.

The inspiration for this phenomenon struck when CFM relaxed copyright and offered a website, Piapro, where fans can remotely collaborate on songs and remixes. In doing so, it created a space for "Vocaloids" such as Miku, Kagamine Rin and Megurine Luka, around which the culture could grow. Next came the MikuMikuDance website, on which anyone can choreograph their own Miku pop videos (there are more than 267,000 on YouTube alone). And as well as the symphony described earlier, Miku has appeared in an entirely computer-generated opera, The End, with costumes drawn by fashion designer Marc Jacobs, which will next be performed in Paris in November.

The virtual singer has made $US120 million for CFM from 80,000 sales plus licensing - partners include Yamaha, Toyota, Sega, Google and Domino's Pizza - and has spawned a subculture whose members worship the art and music they collectively create. Forget cat videos as user-generated content, this is the real deal. "I won't say that Hatsune Miku could destroy the music industry," CFM CEO Hiroyuki Itoh has said, "but I feel like we are involved in something very new."

The biography for Hatsune Miku (which translates as "first sound of the future") is sparse. She's 16, 158 centimetres tall and weighs 42 kilograms. In an interview on YouTube, she says she likes singing, dancing, the colour green and leeks. That's pretty much it. "Miku is free like a musical instrument," an online comment declares. "She belongs to her users, there's no contract saying what, how, when she can sing."

"Miku is popular because she's the world's first wiki-celebrity," says Ian Condry, a cultural anthropologist specialising in Japanese popular culture at Massachusetts Institute of Technology. "Fans can participate in making her songs. It's as if you could write a song for Lady Gaga and she would sing it for you."

"She has no personality behind her save the idea of people," says An Ho, a 29-year-old from Melbourne now working in Japan as an English teacher. "The idea that a character can have whatever personality you choose for it allows for a wealth of creativity."

Rebecca Suter, senior lecturer in Japanese studies at the University of Sydney, notes, "Having a name and just a few traits creates a very peculiar object. She's both an individual, and undefined enough that people can project all sorts of characteristics." Meanwhile, Emong Zheng, 20, a Miku fan and student from western Sydney, says: "She's definitely always happy. I guess she's just the typical teenage girl that anybody would like to be like."

While some producers manipulate her voice to make it sound more human, others add a more mechanical filter. Ho even played a DJ set of uptempo electronic dance music by Miku and other Vocaloid artists at a club night during the recent Sydney Manga and Anime Show. "So many genres are being created," he says. "The crowd went absolutely crazy for it."

Miku's popularity - 10,000 tickets for four Tokyo shows sold out within hours for about $80 each last year - is evident at her concerts, where's she's projected in 3D on to the stage and backed by human musicians. To get a better idea, just look on YouTube. A 2011 performance from the city of Sapporo, for instance, opens with green glowsticks moving like a shoal of fish through the dark, thrusting into the air as one when Miku appears, miming playing a guitar. The stage is bathed in black, purples and reds, and rainbow lasers flash through the air. The crowd screams her name, though she'll never hear it.

Ho went to one performance, and says the age of audience members was mixed, but the reaction was similar to the hysteria which greets teen heartthrobs. "When the concert started, the atmosphere of thousands of fans going crazy was intense. It doesn't matter that Miku and other Vocaloids aren't real. The fans thoroughly enjoy themselves and that makes it a successful concert."

An English-language version of the Hatsune Miku Vocaloid 2 program was launched worldwide last week. Professor Suter doesn't know if the success of Miku will cross over to the English-speaking world, but notes that anime certainly has, and that 90 per cent of Miku's million-plus Facebook fans live outside Japan.

What will attract heavy interest is the way CFM has "squared the circle" in an entertainment industry flailing to cope with digital networks and piracy: they're earning millions while having their customers generate their own entertainment. Miku's not a real singer, but she is a real representation of the collective effort of her followers - and a focal point for their emotional attachment to their creation. And neither is she manufactured like the eventual stars of Australia's Got Talent or Australian Idol - these artists are top-down creations, while Miku's songs are made, and liked, from the crowd up.

"Miku shows a new potential for artistry, and I expect we'll see more experiments in collaborative creativity in the future," says Ian Condry. "The traditional recording industry needs to reinvent itself. This is one of the paths emerging."

In her opera, Miku poses the question: "Will I die?" To which one might answer: as long as one person wishes her alive, the happy, helpful girl in the cerulean pigtails will continue to sing whatever they want, for as long as they want.