Let me clarify something:
- the performer is authorizing the agency to use some rights for a while or for ever?
- the agency is a record company?
- can you give me some feedback to answer your question?
In Spanish we have several contracts for that purpose, but there are some differences: licencia, cesión and agencia, among others.
Well, as a translator, I would use "Autorizacion de Uso de Obra Musical" (it is a license), because the contract purpose is authorize some uses of some recorded materials. You can say that, even when the license is in perpetuity.
However, when a license is in perpetuity and exclusive, it does not seem as an "autorización" or "licencia". In such case, as a lawyer, it would translate as a "Cesión", because you are transfering rights, not just autorizing uses.