Just days after reportedly signing Warner Music Group for its rumored streaming music service, Apple has finally reached an agreement with the final holdout -- Sony Music Entertainment. AllThingsD’s Peter Kafka first reported on the deal this morning, noting that with the big three labels now on board (Apple had previously agreed to terms with Universal), the so-called iRadio service is expected to be announced next week at WWDC.

Specifics of the deal were not mentioned but previous reports have indicated that the per-stream rate Apple will pay to labels is higher than Pandora’s. Additionally the company should provide other revenue channels, such as a quick way for consumers to buy a song they hear and incorporating audio ads into the free service tier.

Apparently one recent dispute with Sony was focused on whether they should be paid for songs that listeners skip. It’s unclear which way the decision went, but despite these licensing details and playing hard ball when it came to negotiations, Kafka says the music industry in general has been receptive to the iRadio concept.

Although the streaming music service will likely be announced at Apple’s WWDC event, it probably won’t launch right away, AllThingsD says. Instead the company could simply go over some of the upcoming features of iRadio, which is described by the site as a free streaming music service that gives users more control over the songs they hear than standard Web radio, but less than full on-demand services like Spotify.