Despite a growing number of streaming music services and outlets to purchase tunes, the digital music revolution is still in its infancy. Apple changed the way we purchase and consume music with iTunes and the iPod and nearly 12 years later, they’re still the industry leader in digital music sales – by a huge margin.

Asymco analyst Horace Dediu now estimates that Apple earns $6.9 billion a year via music purchases on iTunes. When you consider that Billboard’s Glenn Peoples pegs total consumer spending on digital music to be around $9.3 billion, you quickly realize that Apple controls roughly 75 percent of the digital music market.

True enough, services like Rhapsody, Spotify and Pandora as well as other digital marketplaces like Amazon have taken market share away from Cupertino in recent years. It’s a trend that may or may not continue, perhaps depending on how successful iTunes Radio proves to be for Apple later this year.

If you recall, Apple quelled longstanding rumors of a streaming music service earlier this month at WWDC. The music streaming and discovery app, which will be part of iOS 7, will work much like Pandora in that it allows users to create custom radio stations based on songs or artists and share them with friends. Users can opt to purchase a song they want directly in iTunes – a feature that could help maintain Apple’s digital music market share for years to come.

iOS 7 will be available to download later this fall and will likely ship on the new iPhone.