There are two types of royalties for music played on streaming websites such as Pandora: performance royalties (for the performers of the music) and publishing royalties (for the writers/owners of the music).
Pandora pays statutory performance royalties to SoundExchange, as well as publishing royalties to ASCAP, SESAC, and BMI.
Many musicians are unfamiliar with SoundExchange, so please make sure you register here to collect your portion of royalties paid by Pandora as well as other companies that stream music or comedy.
Similarly, songwriters collect their publishing royalties from ASCAP, SESAC, or BMI. They are negotiated separately by all legal music services including Pandora.