Crazy Ideas

Following this premise, and assuming we are only talking about recorded music and not composition. Then oldies would be a very narrow or perhaps even inexistent genre. The first audio recording was in 1857 but it wasn't until 1877 with the invention of the phonograph that we had a reliable method of both recording and reproduction. According to Wikipedia, the verified oldest person is 116, so they were born somewhere around 1909. So, only music recorded in that stretch of time would be oldies. However if we limit further to professionally recorded and commercially distributed music. Then there would be no oldies music, as the first album sold for mass consumption was in 1924, a recording of Tchaikovsky's 1812 overture.

Philosophically speaking it would meant that there's no old music, yet. I find that beautiful and tragic at the same time.