"The sound is just 78 seconds long. It features a cornet solo and a man reciting nursery rhymes, including "Mary Had a Little Lamb." Experts say they have reproduced the sound of the oldest playable recording of an American voice and the first captured musical performance.

It's a recording made in 1878 on a small sheet of tinfoil, then placed on the cylinder of a phonograph invented by Thomas Edison. A hand crank turned a stylus that moved on the foil, recording sound. The foil was donated years ago to a museum in Schenectady, New York, but its significance wasn't appreciated until this summer, when it was brought to researchers in Berkeley."

More information
Details including other movies, photos and all the sound files extracted from scans of the tinfoil can be found here:
http://websnap08.lbl.gov/Tinfoil.html