Asklemmy

Phonographic recording would be incredible to introduce very early on. Basically as soon as the pottery wheel, you could have recorded and played back audio. They'd have to do some fractions-and-guesswork materials science to get anything properly reusable, let alone the ability to press new copies of a recording. But it would get done. Every ruler would want their voice carried to all corners of the territory. Musicians would be known to people who'd never see them in-person. We'd have so much more evidence of how languages were spoken.

But specifically - in the spirit of the question - I'd do this by taking back a crank-operated player and a whole stack of bagpipe albums. Just completely fuck up what ancient peoples think music is supposed to be. Accordions would also work, but I'm not sure I could construct one for demonstration purposes. I could build a hurdy-gurdy, at best. And nobody has a shelf full of vinyl for insufferable droning hurdy-gurdy music.