With iTunes considering going to a subscription model for music, an idea I had way back near the beginning of podcasting before iTunes was even a podcast aggregator..My idea then was to publish some sort of XML that would contain links to the music to buy and the “host/DJ” created audio that would wrap the music and all the info on how to mix it together. Basically a listener would be able to download all the parts and legally purchased music and locally mash them together to make the podcast. It was a way around using licenced music as just the mashed up result would easily be fair use..The big problem would be cross border subscribers not being able to buy the music, mostly just in areas where there was not a system to purchase the tracks in digital form. Although with a bit of work I’d bet some one would be able to work around the issue in a non legal way..So now that iTunes offers subscriptions it’s even easier. Basically anyone who subscribes to the service, obviously has to use iTunes to use it, and the mash up part can easily be built into the application. Publishers just have to upload their audio and link up the tracks they need and any subscriber can add the show to their list and upon release of a new episode the host audio is downloaded as well as the music and the playback is as easy as playing any other podcast..My theory is also supported by a patent that apple applied for a while back for a way of mashing up audio, which at the time everyone thought, and rightly so as it could be used in this way too, that the system would be used to make custom news programs and such.