The problem is that music has no inherent scarcity or exclusivity. Because there's no natural limit to the supply of copies, the marginal cost goes to zero.

To create a viable market, the entire rest of the country/world has to agree to inconvenience itself, simulating a scarcity by saying 'you're the only one who can legally make copies.'

So it's more a matter of hassling everyone else for the benefit of a relatively small group of creators. This is something that can be seen as a value-maximization problem.

How much extra music do we, as a society, get to enjoy by adding another N years to copyright? And what does that cost us in enforcement, licensing, and reduced ability to respin old work?