Already a magnet for tourists and young artists, Berlin is attracting a new generation of Internet start-ups, changing the ways scientists interact or musicians store and share music.
So much so that US Internet giant Google is preparing to open a research centre in the German capital.
Based in the top floors of an anonymous building in former communist East Berlin, for example, SoundCloud, launched in 2008, is one of the fastest growing companies in the music world.
The online platform allows users to store and share music or sound without format restrictions. It jumped from two to three million users in three months at the end of 2010 and has now passed 3.5 million, just by word of mouth.
"We're trying to help anybody to express themselves with sound, whether it's music or the little sounds of everyday life," SoundCloud CEO and co-founder Alexander Ljung told AFP.
David Noel, a 32-year-old German-speaking Belgian, is a driving force in the company, its "evangelist" in start-up lingo.
He explained enthusiastically how the platform has become a tool for academic lecturers, "field recorders" collecting bell chimes or bird songs, or for users who keep and share "sound moments," like the moving voice-mail of a dying relative.
Ljung, a 29 year-old sound engineer born in Britain and raised in Sweden, chose Berlin to set up shop after touring several European capitals.
"Berlin offers a really interesting intersection of arts and very strong technology," he said in a telephone interview from San Francisco, where he has a small office.
Ijad Madisch, CEO of ResearchGate, moved his company from Boston to Berlin at the end of 2010 on the advice of a venture capitalist sponsor, who told him "it's either San Francisco or Berlin."
"But it's easier to find developers and programmers here than in Silicon Valley, where Google and Facebook hire all the workforce," says the German-born virologist and research fellow from Harvard Medical School.
ResearchGate is an online portal which connects more than 800,000 scientists around the world, and expects to pass the million mark in the coming weeks.
Free of charge for scientists, revenues come from institutions advertising for jobs or requiring help to organise events.
"It's very difficult to find answers from experts working in connecting fields, like medicine, biology, or bio-statistics, and to get in touch with colleagues from different countries," said Madisch, 30.
By signing up on the platform, researchers can access publications of interest to them, initiate collaborations, exchange experiences and "negative data."
Scientists publish the results of successful research but not what they did wrong, therefore letting others make the same mistakes, Madisch explained.
The start-up's more than 50 employees come from some 20 countries.
Morgane Hillen, a 22-year-old French woman, said she moved to Berlin without knowing a word of German after job stints in Britain and in Japan.
She works in customer support for ResearchGate, along with Italian, Greek, Norwegian or Spanish colleagues, each in their own language.
SoundCloud's staff has the same international make-up. Sharing office space with another start-up specialised in digital books, its 30-strong staff is a mix of 16 nationalities.
Parker Higgins, a 23-year-old legal expert for SoundCloud, moved from New York to Berlin, "one of the coolest places in the world," he says. "It's a big enough city that whatever you're interested in you can dive into."
Germany's reunified capital is now one of the most visited cities in Europe and its inner courtyards teem with artists exploring music or creating installations.
"A lot of people are attracted by Berlin, Berlin itself is a start-up," said Alexander Ljung. "It's growing fast, it's fairly chaotic. Nobody knows exactly where it's going but it's going in the right direction."
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