I work for Spotify now – so for my Sunday morning programming project I thought I’d write a simple Spotify App that uses The Echo Nest API to create playlists based upon a seed song. I’ve done this before, but the last time was a few years ago and the Spotify Apps API has changed quite a bit since then, so I thought I’d use this as an opportunity to freshen my understanding of the Spotify API as well as to demonstrate how to write a Spotify App that uses The Echo Nest API.

I created an Echo Nest Radio app – it is a very simple app – it looks at what song you are currently playing and will generate an Echo Nest playlist based upon that seed song. The code is pretty straightforward. It grabs the Now Playing track from Spotify, gets the track’s ID and uses that as a seed for The Echo Nest song-radio static playlist API. This call returns Spotify track IDs (thanks to our Rosetta Stone ID mapping layer) that are then tossed into a temporary playlist, which is used to build a List view which is then displayed in the app. All told it is just over 100 lines of Javascript.

It did take me a bit of time to get the hang of the newer Spotify Apps API. It has changed quite a bit since I last used it and many of the examples that I relied on in the past, like Peter Watt’s excellent Kitchen Sink app, use an older version of the API. The new version has some significant changes including a nifty new module system along with a new approach to managing long-running queries that relies on promises. Once I got the hang of it, I decided that I like the new version – it makes for cleaner code and a much more efficient app since much less data needs to be moved around.

The app is on github – to use it you need to sign up for a developer account on Spotify and follow the rest of the Getting Started instructions (this means if you are not a developer, you’ll probably not be able to use the app).

The Spotify Apps API makes it super easy to be able to create apps that run inside Spotify. Its a very familiar programming environment for anyone who has done web programming. You can use all of your favorite libraries from jQuery to Lo-Dash to create really compelling apps that sit on top of the millions and millions of tracks in the Spotify catalog. However, unlike a web app where anyone can publish their app on the web, to publish a Spotify App you have to submit your app to the Spotify App approval process and only apps that Spotify approves are published. Spotify sets a high bar for what ultimately gets approved – which keeps the quality of the apps high, but also means that hacks and experiments built on the Spotify Apps platform will likely never be approved for release to the general public.  It’s a difficult balancing act for Spotify. They’ve built the ultimate music hacking platform with this API, but if they open the doors to every music hack, they will ultimately dilute the listening experience of the user – like so other many App stores that are flooded with garbage apps,  if they publish every app and hack then Spotify listeners would be inundated with the musical equivalent of flashlight and fart apps.  With the approval process, Spotify essentially says ‘the listener comes first’ which is the right choice.   Still, as a music hacker I do wish it was easier to publish rich music apps built on the Spotify platform. Luckily Spotify is committed to building an active and vibrant developer ecosystem so I don’t expect they we will be standing still.

Update 3/24/14: – I’ve added the ability to save these playlists back to Spotify, so you can take the Echo Nest radio playlists with you.

Second update 3/24/14 – note that Spotify’s recent announcement that they are closing app submissions means that you won’t be able to submit apps for publishing anymore, but you should be able to still create your own.