A new partnership between "music intelligence" platform Echonest and streaming music service Play.me lets developers create apps that offer new ways to find music and stream whole tracks for free. The deal can be used to create an app that streams up to five hours a week of music from a catalog of three million tracks; once the weekly streaming limit is reached, users have to pay up $10 a month for unlimited streaming--a pricing scheme identical to competitor Spotify.

Music Explorer FX is just one of more than 70 that already take advantage of Echonest's application programming interface (API), which feeds data to apps from a vast catalog of artists and tracks. The API maps connections between similar songs and artists, is available to any developer who signs up for an Echonest API key. Through the deal with Play.me, Echonest's service can be used to stream tracks from labels including Sony, EMI, and the Orchard. Overnight, online music stalwarts Pandora, Last.fm, and Grooveshark find that they have dozens of competitors built by small teams and even individual coders. "App developers are, we believe, the future of this space, says Echonest's CEO, Jim Lucchese. "They are the future of [music] retail."

Developers don't sell music under the new deal, but they get a cut whenever a user signs up for the Play.me streaming service through their app. This makes them, in essence, sales affiliates for Play.me, and by extension for all the labels whose music it aggregates.

Developers have always been able to cut deals with record labels individually, but that process was prohibitively expensive and time-consuming. By obtaining blanket rights to stream all the music in its catalog, Play.me has eliminated that headache. "From a lawyer standpoint, an API is a very efficient contract," says Lucchese. "It's as if you said, 'Here's my stuff, and here are the rules, and as long as you play by the rules, we're good to go.' "

Using the API that allows access to Echonest's database, five students at Olin College of Engineering were able to put together, in a single semester, a mobile app that explores unexpected connections between bands. The result is the Slice app for Android. The app uses a spinning, color-coded wheel to make it easy to hop from one artist to the next. The goal is to create something more dynamic than traditional Internet radio offerings by giving users a different way to explore the relatedness of artists and genres.