As elsa looks at the shiny mirror  the music began to play as an unknow voice was singing

Insolent boy
This slave of fashion
Basking in your glory

As elsa heard someone singing she decide to sing

Elsa
Angel I hear you
Speak I listen stay
By my side master

Angel my soul was weak
Forgive me enter at last master

Then the unknow voice started to sing his part

Flattering  child
You shall know me
See why in shadow I hide
Look at your face in the mirror
I AM THERE INSIDE

as she look at the mirror she began to sing while walking towards

Elsa
Angel of Music
Guide and guardian
Grant to me your glory
Angel of music
Hide no longer
Come to  me strange Angel

I am your Angel of Music
Come to me :  angel of music

Jack frost : whose that voice

Jack frost : who is that in there

Elsa was reaching her hand towards the mirror as his black gloves reached. Towards her connecting

I am your Angel of Music
Come to me angel of music

Jack frost : Elsa