  Motivated by a promotion to increase the number of musical downloads, we
introduce the concept of $C$-incentive and show an algorithm that compute the
smallest $C$-incentive containing a subset $X \subseteq {\mathbb N}$. On the
other hand, in order to study $C$-incentives, we see that we can focus on
numerical $C$-incentives. Then, we establish that the set formed by all
numerical $C$-incentives is a Frobenius pseudo-variety and we show an
algorithmic process to recurrently build such a pseudo-variety.
