No, but a license may be.
Berne allows for the transfer of rights; specific assignment tends to be considered a contract law issue.
Singing a song in private for personal enjoyment is not considered copyright infringement. However, performing a song in public or recording and distributing it without permission from the copyright holder may be considered infringement.
No, you cannot copyright a voice for commercial use. However, you can protect a voice through trademark or contract agreements.
A website is considered a "literary work" under copyright law.
haydn's contract showed he was considered what
Unless other arrangements are made, the creator of the work is automatically its copyright holder. Ownership can be transferred by contract, or can be inherited. However, transfer of a copyright is far less common than licensing of the copyright.
Claims Court.
Unless other agreements have been made, the creator is considered the copyright holder.
If you opt out and have the right to do so it is considered terminating a contract. If you unilaterally decide to opt out of a contract and do not have a legal basis to do so; that is considered a breach of contract. If you breach a legal contract you can be sued.
In the case of a work-made-for-hire, the copyright would be controlled by the entity that caused the work to be created, rather than the creator. A photographer under contract to a magazine, for example, would not have copyright for those photos.
No, you cannot copyright your voice as it is considered a natural and inherent part of yourself and not a tangible form of expression that can be protected under copyright law.
It depends on the specific language of the contract between the author and the publisher.