The New York Times article "How Pop Sounded Before It Popped" discusses the newly released collection of early recorded music at the University of California. Many recordings are available for free, while the archive is putting out collections of others, such as a 3-volume set of Bert Williams's work. From the article:
Mayhew's record is just one of several thousand cylinders, the first commercially available recordings ever produced, that have recently become available free of charge to anyone with an Internet connection and some spare bandwidth. Last November, the Donald C. Davidson Library at the University of California, Santa Barbara, introduced the Cylinder Digitization and Preservation Project Web site (cylinders.library.ucsb.edu), a collection of more than 6,000 cylinders converted to downloadable MP3's, WAV files and streaming audio. It's an astonishing trove of sounds: opera arias, comic monologues, marching bands, gospel quartets. Above all, there are the pop tunes churned out by Tin Pan Alley at the turn of the century: ragtime ditties, novelty songs, sentimental ballads and a dizzying range of dialect numbers performed by vaudeville's blackface comedians and other "ethnic impersonators."
I'll be adding links to this from the music pages at the Timeline site.