All are integrated directly into Spotify’s desktop app, at no extra cost to the user. Which means that beyond its core streaming service, Spotify is now a platform for developers to create apps on top of its open API (application programming interface, the tech that allows app interaction).

A significant step forward, then, capitalising on what hackers have been doing for a while now ? As our friends at evolver.fm put it, the implications could be huge:

“Think about it: A kid coding away in a basement, anywhere in the world, should be able to build apps within the most popular music subscription service in the world.”

Indeed, with Spotify’s paid subscriber base now at 2.5 million, it is a force to be reckoned with. Despite recent departures of high profile artists and distributors like Coldplay and STHoldings, and ongoing debate over whether the service pays artists enough. midemblog spoke to Spotify’s UK MD about the implications of all of the above.

midemblog: Why is the Spotify apps announcement so important?

Chris Maples: It’s arguably our biggest announcement since we launched. It’s a really significant step. For us, there are only three ways to grow our business: expand to service new markets; cover more devices; or drive more use of Spotify. We’ve had so many requests from day one about adding extra services, be they concert reminders, the possibility to buy tickets or stream lyrics… plus there’s the whole area of semi-curation: getting trusted sources like Rolling Stone or Pitchfork to recommend music. So the launch partners we’ve gone with nicely round off Spotify’s offering.

The recommendation apps should do particularly well: the choice offered by any streaming service can be bewildering for new users…

Some people like a blank canvas, others like a more serendipotous journey. When we first integrated Facebook, you got to see what your friends are listening to; then that feature became real-time; now you’ve got trusted brands curating albums & playlists for you.

midemblog: What was it inspired by? The fact that so many developers have built things on Spotify’s API by themselves?

We saw very early in our history that in the digital age, sharing would be more important than ever. We’ve seen that with our Facebook integration, and from opening up our API almost from launch. This quickly led to the conclusion, when we were looking to build out the service, that our speciality is providing the preeminent music streaming service. Others’ speciality is building the types of services like the apps we’ve launched with today. We’ve had lots of interest from third parties from the outset, asking how they can work with us: so it became clear this was an area of great potential for building value.

midemblog: How did you choose which partners to launch with, and how will future partners be chosen?

We launched with 16 partners and will work will several more. For launch, we focused on those partners who would add value and meet our guidelines, of quality control, for example. The first 16 really respond to the Spotify community’s requests for added features. In the digital world, there used to be a philosophy of ‘if we build it, they will come’. Today, if it’s not good, they’ll go somewhere else.

Looking ahead, we don’t anticipate thousands of requests to make apps. But if developers do want to pitch ideas, they can do so via our website. Once we’ve signed off on the idea, they can develop it.

midemblog: Why don’t developers get a share of your revenues? When will they, if it’s planned?

It’s day one, so for now, app developers get access to our API and our huge audience; and this adds value to our service. We haven’t figured out where model goes yet, but we will be looking at ways we can work that out.

midemblog: How has the initial response to the apps announcement been?

We were number one trending topic on twitter the night of the announcement; but it’s too early for usage stats right now. Besides, we look at engagement, rather than Spotify usage peaks; and we’ve had nothing but very positive feedback so far.

midemblog: When will Spotify apps work in your mobile apps?

The ambition is for the apps to be on all devices, as and when we’re ready. We’re a startup, so we can only do so many things at once; but we are looking to expand to all our users.

mdiemblog: At Wednesday’s conference, (Spotify CEO) Daniel Ek responded to recent criticism – and distributor/group departures – by affirming you’ve paid $150 million back to the industry since launch. Why do artists still earn far less from Spotify than they do from any other format (CD, iTunes)? And why is your platform still worth their while?

We have 15 million tracks in our catalogue, are adding 20,000 new tracks a day and we have fabulous relationships with all our label and licensing partnerss. All relationships go through ups and downs, and we fully respect any label or distributor’s decision to leave.

Our philisophy is free music everywhere, and making sure people are righly rewarded for it. The vast majority of artists feel like they get a fair deal out of Spotify. We just want to continue to give the best possible environment for artists & consumers.

midemblog: Spotify will be present at midem 2012. What are your key objectives in attending?

We want to be front and centre as far as the industry’s concerned. So any event that brings together the music industry, talent and technology is where we should be. We want to build relationships and continue to add value to the music ecosystem, and ensure people understand that.