We are living through the dying days of the CD format. It clings to life here and there, but its usefulness as a medium for transmitting music is pretty much over. What remains is a sort of meta-existence, where the value of a physical music format lies purely in the tactile physicality of the object at the moment of an exchange — before it gets ripped to your computer.
An album can be anything now, as long as a download code can somehow be attached. CDs must compete not only with a resurgence of vinyl and cassettes, but in theory with any kind of merchandise: T-shirts, tote bags even key rings.
Formats aren't solely a means to distribute, however. There are ways of making and experiencing music that grow up and die along with the formats that carry the results. The DJ-driven electronic and hip-hop scenes have helped keep vinyl alive and have, to an extent, reaped the benefits of its revival.