Artists choose what % of the song's royalties to put up for sale. They can also bundle fan experiences, special tracks, digital art - it's all up to them.
You can purchase these streaming royalties in the form of 'tokens', directly from the artist. Any extra bundled benefits will be attached to this token.
Once you've bought a token, you can claim royalties for the song after they've accrued. The time to payout will vary depending on the artist.
If you'd like, you can put your token up for sale on an NFT exchange. When someone else buys this token, they'll get all the royalties and additional benefits that come with it.