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the practice of bribing someone to use their influence or position to promote a particular product or interest
In the case of the music industry, payola refers to influencing charts (and other numeric data also known as metrics) directly by using bribes. Bribes can take the form of both under the table money and/or favors. Blackmail can even be involved. So payola refers to the direct manipulation of Spotify, any of the Korean streaming services, and/or music show broadcast points by using money and/or favors in an underhanded way. Payola does not refer to variety show appearances, getting CFs, etc. because those things don't directly affect metrics.