Sorry, didn't mean to have a contest. 

It's all right.

Forks is kind of a middle of nowhere town and it doesn't take long to get even nowhereier for discreet singing. Bella pulls over onto the highway shoulder. Let's go a ways into the woods and see if you can sing my gem clean.

Okay!

Hike hike hike. Bella holds the arm with the shield on it such that she has a clear look at the diamond-shaped purple gem on her hand. This is like forty-five percent capacity ish. Do I need to do anything but listen?

If you watch I can also dance and then it'll go faster.

...okay. Is this enough space or should we find a clearer spot?

This'll do. I don't know the trees but I shouldn't need to. She looks around. They're healthy trees.

I don't see why they shouldn't be but I'm not sure why that's remarkable.

Sort of the first thing I notice? It matters back home, but for my mother's magic, not mine. Ready?

And she begins to sing. And the sound carries, stunningly so, and she starts to sway to it and then to move to it like it's pulling her off her feet, it might, it's that powerful, and she's grinning gleefully as she sings, happiness, happiness, happiness...

well that's intellectually terrifying but emotionally delightful

Isn't it!

yep that sure is what's going on

(and the gem on Bella's hand clears and pales and brightens and shines like a little purple star)

Hard to say if she's happy it worked or just happy because, you know, song - it affects her too - but that means it worked and they can save the world, she'd probably be pretty ecstatic anyway. 

She stops singing when its color and light stops changing.

That's really something, says Bella, taking a deep breath. Uh, and it worked. ...I forgot to have a recording going, you'll have to record it another time to test next time I'm run down.

Recording?

Uh, another not-magic-but-you-might-mistake-it thing, we've got stuff that can look at and listen to things and then reproduce them later.

Oh, cool, so then all the magical girls can have it and I won't need to run around singing nonstop!

Nor stay here if you'd rather go home, nods Bella, because I can keep objects between loops if I fit them in my shield.

I should go home, everyone will worry, except - 

what kind of magic do magical girls have, anyway? Once we've saved your world, any chance you could have a shot at mine?

It's pretty freeform but it has to fit within the gem capacity. ...I guess if you were actively singing at me it'd be more a matter of my ability to concentrate on doing magic and whatever the actual recharge versus expenditure rate was? I'm not aware of limits other than efficiency and total capacity, there could easily be some, those are usually pretty sharply limiting. Most puella magi cannot stop time like me because it would be so inefficient if they tried it it'd witch them on the spot, not because that's a special thing only I get to do.

If there's a short window to send me home I guess I'll go once you have your recordings - as many as you need, or can you have them copied? - but if there's not, I want to stay here and once we've fixed your world figure out whether we could take on Morgoth. And then you could come with me and do that.

I don't really know how the loop will work for edge cases involving other worlds and stuff. I can copy the recording infinitely. If you were not going to wish into the loop you'd need to be out by the end of the month, because if I reset without you it seems likely that you'd just - cease to exist - but if you're looping with me you'd probably be at least as portable as I am, from there, so if we get past the point where the witch eats the world and maybe address the evil aliens I would be happy to go save another planet.

Great! Then let's try to get me looping with you. Even though I don't think I could cease to exist.

Okay. How old are you and does that song work reflexively?

It works on me, yeah, and like five hundred?