Spotify/Algoriddim

You don't have to be professional DJ to use the app djay 2, but now you can sound much more like one.

Sweden-based subscription music service Spotify on Thursday added its catalog of more than 20 million songs to djay 2, one of the most-used DJ apps for Apple's mobile operating system iOS.

"I was shocked how obsolete I was," said Karim Morsy, whose career as a DJ and study of computer science led to co-founding djay 2's developer parent, Algoriddim. As software took the technical difficulty out of many DJ tricks for a mainstream audience, the remaining barrier was giving the masses a giant catalog to play with, since most DJ apps are limited to the digital songs you've already purchased outright. Morsy compared it to an app not only teaching everyone how to cook well but also giving everyone an nearly unlimited pantry of ingredients.

Djay isn't the first DJ app to integrate a subscription music service -- in February, Spotify itself integrated on the Pacemaker iPad DJ app -- but it represents the strongest one-two punch of the combination so far, merging the biggest subscription on-demand streaming service with one of the most popular DJ apps, at more than 10 million users. Wednesday, Spotify said it has surpassed 10 million paid subscribers, affirming its lead in the burgeoning on-demand streaming service race.

Despite its growth, Spotify has struggled to get the attention of mainstream audiences, particularly in the US. Partnerships like the one with djay 2, which attracts a big base of casual music lovers, are moves to help cross that divide.

Spotify said the capability to DJ with its service has been something users have asked for for years. "It's an opportunity for us to introduce Spotify to djay's 10 million users and hopefully get them to become Spotify subscribers," the company said.

The Spotify-integrated app, for iPhone and iPad, is available as a free update to all existing users of djay 2, but you need a Spotify Premium subscription -- $9.99 a month -- to access the catalog. All djay 2 users can get a free seven-day trial of Spotify premium, and the app for iPhone will be free during the week of its launch. It usually costs $1.99. The djay 2 app for iPad is normally $9.99 but will cost $4.99 for the update's launch.

The partnership includes features like "Match," which uses technology from Echo Nest -- a music-intelligence company that Spotify bought in March -- to recommend tracks that go well with what is already playing, based on danceability, beats per minute, key, and music style. Another new feature is "Automix Radio," which both picks tracks that go well together and then automatically mixes these tracks with beat-matched, DJ-style transitions.

The Spotify integration will also adopt the existing playlists, starred tracks, and inbox for real-time song requests to the DJ in the app from Spotify, as well as search, top lists, and the ability to browse by genres or moods. The app can toggle between Spotify songs and iTunes songs, as well as mix tracks from both. It also allows users to share their set lists as Spotify playlists via SMS, email, Facebook, and Twitter.

Spotify said that no money changed hands between the new partners but that Spotify will -- of course -- make money from any new premium subscribers brought on board by the new features.