Leasing Rights
If any music artist has leasing rights for a beat then lease rights give the music artist a certain amount of uses per lease. Once the lease runs out then the customer would need to buy another lease for the same beat. It’s all up to you that how many units you want to give out.
Another main thing about a lease is that producer can sell the beat to multiple artists as long as no one buys the exclusive rights to that particular beats. Selling beats on the lease would be good for the producer as he won’t have to take the beat off sale and be able to make more money off of it.