My impression is that Ujo is a smart contract service, and that Spotify would be a party to a contract. That is, Ujo gets a cut (or fee) for contract creation and management, and Spotify could earn a cut of a contract by making songs available on their streaming service. A t-shirt company could sell band t-shirts similarly by making a contract with the artists via Ujo. The royalty payout system is decentralized, but contract creation wouldn't need to be, and in this case, probably wouldn't benefit from it. Of course, you could have decentralized contract creation like Lighthouse, but you lose a lot of incentives that provide for ease of use and adoption.
Perhaps someday someone will make an OpenBazaar for music, but I don't know how you could be sure you were paying the genuine artists unless there was a trusted attribution database somewhere, I see Ujo as trying to be that database.