All-you-can-stream music service Spotify is letting third party developers expand on its functionality using its API. It is offering the results to users in a new HTML5 app directory, CEO Daniel Ek announced today in New York.

Developers have already built apps with features like the ability to find and purchase concert tickets, the means to display a song’s lyrics on-screen through TuneWiki and deeper Last.fm integration for better music recommendations.
During today’s presentation, Rolling Stone cofounder and publisher Jann Wenner took to the stage to sing Spotify’s praises, just before Ek unveiled the application that Rolling Stone built to work within Spotify. It takes publication-curated playlists to a new level with a rich HTML5 interface and more room for editorial content.
The move attempts to rebrand Spotify as more of a platform, much as Facebook once did when it opened up the ability for developers to build applications on top of the social network. It’s a wise move for Spotify, which faces a rapidly-expanding user base and only a limited capacity to roll out new features itself. By opening up its platform to developers, Spotify allows for more rapid innovation without distracting itself from the core product.
Other available apps include SongKick, The Guardian, Billboard and Soundrop, presumably with plenty more to come. Any developer can code apps for Spotify but they do have to be approved by the company before appearing in the directory.
Slowly Opening Up Spotify’s Walled Garden
The catch? For now, the new third party apps are only available on the desktop client, although Ek did indicate that popular features would find their way onto the company’s mobile apps.
There’s no word on whether the same JavaScript API used by Spotify app developers would be available to everyday Web developers. This would enable music publications and other music-related websites to create an experience much like Rolling Stone has done from within Spotify, but they could do so on the open Web. Of course, one of the obstacles to a seamless experience is the fact that Spotify does not have a Web app of its own, requiring a native desktop or mobile application for song playback.
Spotify first launched in the United States in July, after a prolonged and anxious wait by American music fans, who had been hearing more than a little buzz about the European music service. Today, the company has 2.5 million paying subscribers, Ek said.
Today’s announcement comes just two weeks after the public launch of Google Music and Apple’s iTunes Match. While neither service is a director competitor to Spotify’s freemium streaming model, the two tech giants are inching closer to the space and upstarts like Spotify need to be on their guard.