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.

Here's a darkly hilarious one, because you could do it by accident: give smallpox to the native Americans a few hundred years early. Right around 1000 AD, show up to shake hands and teach metallurgy or whatever, maybe planning to jump-start their resistance to colonization... and their resistance to slaughterhouse-borne diseases, the hard way.

This would of course completely fuck up their population numbers, much the same as would happen in Europe in the 1300s. But by the time Columbus showed up to be the absolute worst person who could possibly discover a new continent, they'd be largely recovered, and they'd get to trade whole new strains with the seasick lemon-sucking weirdos who kept asking where the spices were. The returning ships would offer tomatoes and potatoes and another Black Death. Hopefully preventing Malthus from being such an influential bastard, and causing the first engineered famine in Ireland, whose population did not recover from the potato famine until this century.

New England colonies would presumably still take hold, but wouldn't steamroll all the way to the west coast. Hopefully they'd be limited and northern enough that slavery is less prevalent, less absolute, and - ironically - still a matter of trade. Because what ended the triangle trade to America was the treatment of African captives as livestock to be bred. The politics of this alternate timeline would be hilariously complex compared to now, and probably result in more and stranger wars than we can imagine, but there would be so many averted times where atrocities happened, effectively unopposed.

id give the taino a flak cannon to shoot at colombus

i'd write everything shakespeare did before he did

I want to say leave a modern computer or some other piece of technology at some point in time (maybe 50's) but I'm not sure if it could be reversed engineered

Avoid cocaine Limit my drinking Focus in school better instead of partying Go therapy Been patient enough to grow a meaningful relationship with someone special but I was too egoistical to see it then Learn music Workout and not gain weight from excessive drinking and eating

I'd love to see Socrates as modern day politician

Bring a time machine with you and teach ancient Egyptians how to use it

i'd go kill all the tiktaalik or maybe whatever the first common ancestor eukaryotes were

Teaching Abraham Lincoln how to do egirl makeup and being a femboy.