"Where do you think it goes?"

Let's assume the kid knows it's a recording. It's still a valid question.

Like where is the recording coming from when the kid asks Alexa to play a song?

I never thought about it, as I don't have kids, but must be a bit harder explaining a global IT-infrastructure than it was for my grandpa to explaining how a VHS works. On a generalised level, that is.

The music stays in your head until your forget it. Music only exists in your head

All these physics answers! The funnest explanation for a kid is just that music is only there when you're listening to it. If you don't listen, there's no music. When you start listening again, music comes back. Then ask if they can hear the music of the wind.

To retire on a farm upstate, unless my mom lied to me 🤔

It goes on until it doesn’t? Seems like there’s a pseudo-scientific philosophical argument that it continues on forever at some quantum level?

into our minds and into our hearts

Nothing's really ever gone

The music stays there we keep moving

They should show their kid this.

But actually though, music goes up into the sky and becomes clouds.

It diverges into the quantum realm of misheard lyrics.

As someone with a degree in Philosophy, I don't think this is really a philosophical question. The science is interesting and useful to know