Many years before Edison the French Scott de Martinville worked with success on the recording of sound. Since he was only interested in recording and not in replaying what was recorded, his invention was forgotten. Researchers now have used the recording and found a method to make audible what was recorded.

What we can hear now is 20 years older than the until now oldest known recording. And it is the French folksong Au claire de la lune.

Article with an audio of the oldest folksong recording (The article is in German. You'll have to scroll to find the audio)

Wolfgang