Jeez everybody has used limewire at one point in time 
ive only used Itunes and CDs.
As for music copyrights:
Music copyright laws in the United States grant composers and lyricists exclusive rights to their creations for a limited time. This limited time is defined as such:
* For musical compositions that were created after January 1, 1978, the copyright will be in effect for the duration of the life of the longest surviving composer/copyright owner of the work plus another 70 years.
* The copyright of musical compositions registered before January 1, 1978 will be in effect for 95 years from the date it was registered.
* The copyright of musical compositions registered before January 1, 1923 will be in effect for 75 years.
Public Domain
Any songs that are not under copyright are said to be in the public domain. Restrictions of reproduction, publication, public performance or rearrangement no longer apply to these works. A song's copyright can expire--like those that were made before the year 1923--or the composer or lyricist can renounce his exclusive rights either during his lifetime or after his death. To determine with certainty that a song is in the public domain, it is necessary to check the copyright date (which, in sheet music, for example, is commonly located on the first page or title page).
Basically alot of the music listened to in the 40's (including classical and 20's and 30's music) could most likely be public domain by now and free to use