We do all talk about works created before 1923 as being in the public domain and sometimes we wiggle our hands to signify that there are exceptions. Here Hirtle documents a problem with a well known piece of music. There is lots of quotable text in his post, but this one gets at the heart of the matter:
In short, just because a work was published in the US prior to 1923 does not mean it is in the public domain. The first authorized publication needs to have occurred before that date.
Technorati tag: Copyright