One way in which music could be "paid for" by downloaders is by setting a compulsory price (while presumably also making it impossible to download through outlets that will not engage with that pricing). This essay from Patry copyright blog discusses the legal ramifications of compulsory price-setting.

But as it points out, the four largest record companies also own and control the four largest music publishers. All eight enjoy a combined market share of around 70% to 80% of all music. As close as they are as family, the record companies and their music publishers have managed to tied up the committee and the Copyright Office for years trying to broker terms for their latest “compulsory” license.

Personally, even before the conversation with big music publisher who said publishing was fantastic because so many of his clients were idiots - "and, anyhow, it's money they wouldn't have got otherwise" - publishing looked to me looked like a cartel.

It's not precisely price-fixing.

But a bunch of people know how it works; they keep that information to themselves; as a result, they make remarkable profit in return for a little simple admin work chasing payments for musicians; and funnily enough, it never quite becomes possible for the musicians to chase those payments themselves and cut out the middleman. They don't have "the relationships", apparently.

It's not an attitude that encourages trust.

Hence, according to Patry - Some reasons for the [American Department of Justice] to be [part of a compulsory licence negotiation]:

(1) Every compulsory license is by definition anti-competitive in origin. It exists because there was no competitive milieu in which an adequate license could be fashioned.

(2) Ultimately, every compulsory license results in an aggregation of commercial users, an aggregation of owners or both to argue the rate and to distribute the proceeds of the license. These are powerful collectives inherently capable of mischief. (Some like ASCAP and BMI are already under court supervision as an antitrust matter; but other more ad hoc collectives are not, such as SoundExchange.)

(3) These collectives carry even greater market power because they enjoy broad statutory anti-trust exemptions in order to participate in the rate setting process.

(4) Finally, all compulsory licenses impact businesses well beyond the scope of the license itself. Someone needs to take a long view inside the rate proceedings to argue the impact of price and terms on competitiveness and on adjacent open markets. That isn’t happening now.