There’s a growing number of polished DJing apps for Apple’s iPad, but they all rely on music stored on the device. What about DJing on an iPad drawing music from a streaming service like Spotify or Deezer? That’s the idea of a new, free iPad app called DJ Mixer for Spotify, which launched over the weekend. Developed by Musicsoft Arts, it’s a Spotified version of its existing DJ Mixer app that gets people to sign in to the streaming service and transfer across tracks to spin on its virtual decks. Features include cross-fading, EQ and effects, loops and hot cues, as well as the ability to record mixes and upload them to SoundCloud (yes, hello copyright police…) And while it’s drawing on a streaming service, the tracks appear to be cached on the device – we had DJ Mixer for Spotify working in airplane mode – so there’s no concern about audio suddenly dropping during a set. It’s a little rough around the edges, but our main question is how the free app’s business model will work: it uses the Spotify Core API, which we think means they’re barred from ever charging for the app.