Gregorian chants. Although the people singing aren't (
![Cheeky [:cheeky:]](/emoticons/cheeky.gif)
), the song itself (or at least, type of music) is over a thousand years old. The oldest known music. (although apparently
this beats it by another thousand years.
If that doesn't meet your vague criteria and it needs to be something recorded, then I guess I suppose it would be old piano recordings on some of Edisons early recording devices. Johannes Brahms probably.
The only thing worse than beating a dead horse is betting on one.