What happens if someone lists in his/her will that his/her estate will be equally divided among his/her children, and the estate includes a copyright (specifically to a music recording)? Do all heirs need to give consent for a copy to be made? Just one? A majority?
A copyright can be divided into as many pieces as the owners choose. Initially, all authors have a share m(an equal share unless they have an agreement on some other share arrangement), But each author (or later owner) can leave the copyright to multiple heirs, in equal or unequal shares. Each owner can sell all or part of the copyright (or usage rights) to one or more new owners.
Under US law, any co-owner may permit a copy (or copies) to be made, or may grant a non-exclusive license. However, the co-owner doing this must account to the other co-owners for any profits made, and share them according to whatever agreement the co-owners may have (by share if there is no other agreement). But to grant an exclusive license, all co-owners must agree.
The law in many other countries is different. In some countries, a majority of owners (by share usually) must agree to grant even a non-exclusive license.
The co-owners may make an agreement to limit granting of licenses to some particular owner or representative or to require wider consent than a single co-owner.