Listen to the Past
Listen to diverse musical expressions from people around the world and across time:
Smithsonian Folkways
Smithsonian American Song
Smithsonian Global Sounds
Folksoundomy
Old Time Radio
Live Music Archive
Library of Congress, Oral Histories of Americans
Milkin Archive of Jewish Music
American Archive of Pubic Broadcasting
National Jukebox
American Routes
Here is a long list of archives with digitized collections featuring sound recordings.