Parisian Édouard-Léon Scott de Martinville is the first person to have ever captured sound, and also the first person who recorded a human voice in the form of a short musical recital (most likely his own). In 1857, Scott patented the Phonautograph, a device that funneled sound waves through a horn with a stylus on the end that scribbled them into tracings on a revolving cylinder. Scott had no idea that sound recordings could be played back as he only sought to make visual recordings of the audio. Scott recorded the French folksong "Au Clair de la Lune" into a phonautograph on April 9, 1860, the first audible recording of a human voice in history.
Incredibly, thanks to modern sound engineering, the recording of "Au Clair de la Lune" can be heard pretty clearly. Even more amazing is this video of the live 'cleaning' process that shows the transformation of the original warbling sounds recorded to something we'd recognize as a distinct song with decipherable words: