Apple (S AAPL) is still dominating the digital download business, with eight out of ten digital music buyers getting their tracks from iTunes in the fourth quarter of 2012, according to new numbers released Tuesday by the NPD Group. Volume-wise, Apple sold 63 percent of all digital tracks in that quarter, followed by Amazon (s AMZN) as a distant second with 22 percent. Apple wants to maintain that lead and keep its digital download biz healthy — and that’s why it’s looking to launch its own streaming service soon.

iRadio, as the service has been called by some, will reportedly mimic the functionality of Pandora, (s P) offering users continuous streaming with limited interactivity. The company is negotiating directly with record labels as opposed to relying on the type of compulsory licenses that are at the core of Pandora’s business model. That means that Apple might offer its users…