Sound recordings fixed in a tangible form before February 15, 1972, are not subject to federal copyright law in the U.S., only state statutory law or state common law. In Wisconsin, copying sound recordings is a copyright violation only if it is done for “commercial advantage or private financial gain” (see § 943.207, “Transfer of recorded sounds for unlawful use”). Although “private financial gain” is not defined in that section, other sections (for example, § 943.46) of that chapter say,
All right, music aficionados, I want to bulk up my classical music collection in Wisconsin, but legally. Name some great performances of music works that are in the public domain (any work published before 1923), that were recorded before Feb. 15, 1972. An example would be the Maria Callas recording (1964) of the opera Carmen (1875).