This week, darling of the all-you-can-stream music space Spotify announced that it's opening up to third party developers and creating a platform on which they can build HTML5 apps to run within its desktop client. Once approved by Spotify, those apps will be available to users from the service's new "App Finder" button. They've also added a new home screen that show's what music is trending among one's friends, as well as an improved social experience all around.

The new features are not yet included in the Spotify desktop client, but curious users can download a preview of the next version of the software. We did and after using it, we're finding that the inclusion of third party apps makes Spotify much better.

It's not that Spotify was lacking to begin with. Aside from arguably needing a better user interface (see Rdio), the service's desktop client is great for streaming music and a few other related tasks. One thing that Spotify has always sorely lacked, however, is a music recommendation engine. For that, users have had to rely on scrobbling to Last.fm or other third party hacks. With this latest update, all of that changes.

Of the dozen or so apps that launched with Spotify's new platform, many of them are geared toward discovering new music, whether via human tastemakers or by algorithm. Reputable music publications like Rolling Stone and Pitchfork have apps, which further bridges the gap between the reading published reviews and actually hearing music.

Critic-curated Playlists from Top Publications

Pitchfork's app takes the experience of reading reviews and best-of lists from the influential publication and bakes that directly into Spotify itself, enabling immediate playback of the albums you're reading about. The app opens up to Pitchfork's "Best New Albums" list, from which any of the albums can be streamed (assuming they're available on Spotify, which most are). From there, you can browse the rest of their audio-enhanced reviews and view their repository of Spotify playlists, which include many the site's best-of roundups like the Top 500 tracks of the 2000s and the Top 50 Singles of 2003. Throughout the experience, almost every song you see listed can be heard and albums and lists can be added as a Spotify playlist for later listening.

The Rolling Stone Recommends app is a pretty similar concept, just from a more mainstream editorial perspective. All of the magazine's recent top-rated albums and songs can be streamed and the app offers playlists that tie in with recent features in Rolling Stone, such as the top guitarists of all time. The Guardian offers an app of its own, again based on the music its critics have recently reviewed.

Songs Recommended Based on Your Listening History or Mood

Professional critics aren't the only source of music recommendations on the new platform. The desktop client is now deeply integrated with Last.fm, a service that has long provided recommendations based on one's listening history. It can track every song you listen to in iTunes, Spotify and a variety of other services and devices and then serve up music based on what you're most likely to be into.

Rather than just letting you "scrobble" songs off to some other island called Last.fm, Spotify brings much of the Last.fm Web app's functionality directly into its desktop client. The "Overview" tab displays your vital stats: most listened-to albums, recommended music, loved tracks and recently scrobbled tracks. The "Now Playing" tab focuses on the music currently being played, whether it came from the Last.fm app or elsewhere, and give instant access to similar artists.

The "Recommendations" tab drills shows an expanded view of what's recommended on the app's home screen. This is where most of the magic happens. Each recommended album can be streamed instantly or added as a playlist within Spotify. As it's always done, Last.fm identifies exactly why it's recommending each album. Sometimes it's because you've listened to several similar artists, or perhaps you've already heard one release by that artist and want to hear more.

The functionality itself is nothing new. This is what Last.fm has done for years. But now that it's baked right into Spotify, it enables you to stream every recommended song or album in its entirety, all from a single interface.

If you're already a Last.fm user, the addition of this app alone blows the old Spotify experience out of the water. The integration breathes new life into Last.fm while making Spotify a much more useful service.

Another service that's available as an integrated app is Moodagent, a service that recommends music based on very specific musical qualities such as tempo and mood. It allows Spotify users to choose any song that happens to suit their mood at the moment, and then automatically build out a lengthy playlist of songs that are likely to evoke the same emotional response.

This is Just the Beginning

Other apps that are launching with the new Spotify platform include one for music aggregation site We Are Hunted, social listening service SoundDrop and Billboard. Songkick shows upcoming concerts by artist you've listened to, while TuneWiki displays lyrics in time with when they're sung during a song.

As much value as these apps add to the experience of using Spotify, it's really just a handful of partners the Swedish service has opted to launch with. This is really just the beginning. The platform is now open to developers, who can use the same HTML5 and JavaScript they're accustomed to using to build Web apps. Spotify is requiring apps go through an Apple-style approval process, but hopefully it won't be unreasonably rigorous and will help to keep the directory clean of useless apps and malware.

Developers are wasting no time getting started. Andy Smith, creator of an Echo Nest-based recommendation app for Spotify told us he's working on an official version for Spotify's consideration. For developers who want to start coding apps for Spotify, Music Machinery has a detailed introduction to the process. Be warned, though: for now the company is not offering any kind of revenue share to developers, as all apps are free to install.

The digital music space is a busy place these days, from tech giants launching cloud storage lockers and streaming services duking it out, to developers all over the world participating in music hack days and building new and interesting things everyday. As Spotify grows into its new role as a platform, we expect to see nearly limitless new integrations and features added as time goes on.