Pandora is an Internet radio-style streaming site. (Fair warning: like many streaming sites, it is only accessible in a handful of territories.) As such, its URLs should be linked via the "stream for free" relationship.
Example of an artist page on Pandora: http://www.pandora.com/blacktop-mojo
Example of a release page: https://www.pandora.com/blacktop-mojo/i-am