some thoughts...
Does anyone know who is being investigated? Record companies or internet download retailers?
The gubment (1) could be targetting a conspiracy among record companies against online retailers, or (2) they might be going after a conspiracy with online retailers against consumers.
I can think of scenarios for each. The first takes some leaps of thought to construct. The record companies were so exceedingly reluctant to sell for download, and the online retailers so eager to gain access to songs, that the record companies could essentially refuse to negotiate. This would enable them to engage in anti-competitive practices by setting industry standard prices and getting around explicitly fixing prices by pointing to an industry standard precedent that no record company was willing to deviate from.
The second is an obvious one, but seems unlikely. Apple sells songs for one price (a fixed price), yet I don't think that price fixing has anything to do with fixed/single pricing schemes. I couldn't see dollar stores (if everything were actually priced at a dollar) being a target.
In my opinion record companies have been ripping everybody off for a long time, but it still seems like their right to do so if there are customers who are willing to waste hard-earned or hardly-earned cash. I don't see why a market-encouraged rip off would not extend to the online world.