Rock Band's emphasis on downloadable songs was partially inspired by the popularity of iTunes, according to Harmonix creative director Josh Randall.
While chatting to Randall at E3, we asked the developer if he could ever see Rock Band taking on an iTunes-like format, with a constant stream of DLC replacing the current trend for a new game each year.
"It's pretty close now, right?" he said. "I think Rock Band has the most DLC of any console game ever made, so I think that sort of model [iTunes] was certainly an inspiration for the game."
Randall added that it's the visual element of rhythm games that requires Harmonix to rely on physical media.
"I think the other component you have to think about is that it's pretty easy to download a song that's a certain file size and that has all the note data and stuff. But then you need the visuals to match up with, the full environments and all that, and right now that stuff fits on a DVD or a Blu-ray or whatever."
The developer concluded it might be easier for people to download this content once domestic internet connections are improved.