The term "master rights" comes from the word "master tape". On the master tape is the original tape recording that comes from the recording studio and is finally forwarded for replication, e.g. to a pressing shop.

In order to release a song, you need to have the master rights.
If you have recorded and produced a song yourself, you automatically own the master rights. If, on the other hand, you have a song produced by another producer, you need the written consent of the producer to be allowed to publish the title.
Generally, producers and labels get the master rights when they finance and produce the recordings. Artists can keep the master rights if they produce independently.
Artists, labels and producers may share master rights depending on how the recordings were produced and who was involved in their creation.

Master rights are of great importance to the music industry because they allow the rights holder to control how and where the music is used. It is important to clarify the rights to the recordings before they are released.