Hmm, I'd say take out the worry and let someone have plays until he plays it so many times it actually buys the track. Say you needed to play 20x and then it is bought or you could buy it for less immediately :)
This could be a good subscription service. Like Patreon you money would go where you are most engaged but you'd pay a fixed amount each month. Maybe for bands to gain a fixed income you'd have 3-4 bands each receiving 1-2 dollars a month and the rest you could play anything you'd want.