I read this on a site on copyright:
"Generally copyright in music and lyrics lasts for the life of the author or creator, plus 70 years after the end of the calendar year in which the author dies.
If the work was not published, broadcast, performed or records of the work had not been offered or exposed for sale to the public until after the creator's death, copyright will last for 70 years from the end of the calendar year of first publication, broadcast, performance or when records of the work were offered or exposed for sale to the public."
This is a lot longer than what WizardSleeve mentioned of 50 years after the copyright was made. Which is more accurate. And also, when a copyright expires, does that mean that an artist can legally sample from a recording of the until recently copyrighted songs, or is it just for covers of the same music? I'm thinking of the drum breaks and if artists sampling a break from a particular song, whether they could take a larger portion of the song, the main riff, for example?