Works enter the public domain when copyright expires, when the creator dedicates them to it, or when they were never eligible for protection. Terms depend on country: in the United States, works published before 1931 are in the public domain as of 2026.
A composition can be public domain while a particular recording of it is still protected. Bach’s Goldberg Variations are free to perform, but each recording has its own rights unless the performer released it freely, as Kimiko Ishizaka did with her Open Goldberg Variations.
Using it in a prompt
Not a prompt term. If you want a traditional melody in a generated track, check that the melody itself is public domain.