Help:When does music enter the public domain?
A piece of music enters into the public domain a certain amount of time after it's first written. But the time interval is different in each country.
In the US, all music published before 1923 is now public domain, and much music which was not renewed since then is also in the public domain. Also, facsimiles of original scores and older publications are not copyrightable. However, there are exceptions.
In Europe the general rule is that copyright protection exists until 70 years after the composer's death - though sometimes the copyright persists because it is owned by a publisher or by the composer's 'estate' rather than by the composer himself.
The rules and exceptions are very convoluted, so do not take these general guidelines as legal precedent in any way.