It depends on what jurisdictions you are dealing with.
For the UK, according to PRS:
"Copyright in original musical, literary, dramatic and artistic works lasts until 70 years
after the death of the author. The copyright in films also lasts for 70 years after the
death of the last to survive of the principal director, author of the screenplay and
dialogue and the composer of the music created specifically for the film. Copyright
protection in sound recordings and broadcasts exists for 50 years from the end of the
calendar year in which it was made or released. Copyright in the typographical
arrangement of published editions exists for 25 years from first publication.
Where the work has originated from outside the European Economic Area (EEA) or
the author is not an EEA national the situation is slightly different. In this situation
the copyright will generally last for as long as the work attracts copyright protection
in the country of origin (usually the country where the work is first published) or if
not published, the author's national country as long as that period does not exceed
the period for which UK copyright law protects works of EEA origin."
Here's a link to the original document:
https://www.prsformusic.com/SiteCollectionDocuments/Copyright/Copyright_Law_Introduction.pdf
In the US:
"How long does a copyright last?
The term of copyright for a particular work depends on several factors, including whether it has been published, and, if so, the date of first publication. As a general rule, for works created after January 1, 1978, copyright protection lasts for the life of the author plus an additional 70 years. For an anonymous work, a pseudonymous work, or a work made for hire, the copyright endures for a term of 95 years from the year of its first publication or a term of 120 years from the year of its creation, whichever expires first. For works first published prior to 1978, the term will vary depending on several factors. To determine the length of copyright protection for a particular work, consult chapter 3 of the Copyright Act (title 17 of the United States Code). More information on the term of copyright can be found in Circular 15a, Duration of Copyright, and Circular 1, Copyright Basics. "