LISTEN Demi Lovato New Song 2013 'Heart by Heart' from 'The Mortal Instruments: City of Bones' Soundtrack: Powerful Pop Ballad Perfect Dramatic Fit Upcoming Teen Movie [AUDIO]

Demi Lovato's new song for "The Mortal Instruments: City of Bones" soundtrack, "Heart by Heart," has finally hit the web in its full length.

The powerful ballad was first teased with a snippet in early July, where the true power of the song was yet to be revealed.

"Heart By Heart" begins with a soft, slightly haunting piano riff before Lovato's vocals come in. "When your soul finds the soul it was waiting for / When someone walks into your heart through an open door / When your finds the hand it was meant to hold / Don't let go," the "Warrior" singer croons in the first verse.

The song continues to build and swell into a powerful pop ballad with gritty dark rock undertones. Each verse and its following chorus pack a bigger punch. By the end of the song, Lovato's voice soars above the dramatic, rich instrumentation. The final chorus features some of the most powerful vocal runs from Lovato to date.

The final result is a monstrous ballad, perfect for the upcoming teen flick about a demon-fighting girl.

Listen to the full version of Demi Lovato's "Heart By Heart" below.

"The Mortal Instruments: City of Bones" soundtrack, which also features songs from Zedd, Ariana Grane & Nathan Sykes and Jessie J, will be released on Aug. 20. The film will hit theatres the following day.