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The ERN message was not specified to convey any information about the current rights holders of the musical works used embodied in Resources (and, thus, used in Releases). As a consequence, there is no means to determine, from an ERN message alone, whether a musical work embodied in a Resource is in the public domain or, if it is, in which territories it is in the public domain.
"Public domain" is a term used to denote that a musical work (or indeed a sound recording) is no long longer protected by copyright in a specific territory, usually as a result of the effluxion of time.
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