SOLVED. Children/ YA Fantasy. Read no later than 2013. Orphans must mine seemingly worthless rocks. The rocks are a very good fuel source and explode when someone has fear in their voice. [s]

[Alvin]

In the book, the orphans are forced to work in the mines to gather some kind of rocks. The main character (a girl) is not an orphan but spends time around the mines/orphanage for some reason, I don't remember why. The main character is good friends with one of the orphan boys and he is with her through out the entire story.
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The main character realizes that these rocks are explosive and can be used to fuel machines. She shares this info with her friend.

You can make them explode/function by hitting a certain note with your voice. The main character tries to mimic this pitch and fails. Later on in the book, she is in a dangerous situation and screams, the rocks around her explode.
She realizes that there has to be a tinge of fear in your voice to make the rocks explode/fuel machines/function. I don't remember the majority of the plot but at the end of the book, the main character tries to use a machine, but she is no longer able to make the rocks work because she has no fear.
Her orphan friend helps her out and starts the machine for her, this is because he still has fear in his voice. The orphanage/organization that was forcing him to mine the rocks is gone now and he isn't sure where he will go now. I think the main character's father offers to adopt him.

[Rainbowheart]

The Copper Elephant?

[Dippy]

I know this one for sure, the main boy had a like dumb friend who could sing really well named Danny hang on let me find the name

[Dippy]

I remember this one so vividly I swear I know it

[Dippy]

The Secret of Zoom!

[Rainbowheart]

The Secret of Zoom for Dippy's suggestion.

[Alvin]

Dippy wrote: "The Secret of Zoom!"

Yep, you got it! Thanks alot!