Demi Lovato releases 'Heart to Heart,' her single from the Mortal Instruments soundtrack.

Demi Lovato releases ‘Heart to Heart,’ her single from the Mortal Instruments soundtrack.

Demi Lovato has released her new song “Heart By Heart,” It’s included on the official soundtrack for “The Mortal Instruments: City of Bones,” a fantasy sci-fi film based on Cassandra Clare’s first book in her “The Mortal Instruments” series.

The movie stars Lily Collins, Jamie Campbell Bower, Kevin Zegers, Jemima West, Godfrey Gao, Lena Headey and Jonathan Rhys Meyers.

The story focuses on Clary Fray (Collins), a teen who witnesses a murder at a club. She discovers that her mother, Jocelyn (Headey), was also attacked in their New York City home and kidnapped by a man named Valentine (Meyers). She learns that he’s searching for the Mortal Cup.

The movie delves into a fantasy world where Clary learns that her mother was a Shadowhunter, a half-angel, half-human warrior with super natural powers. Clairy also has her powers and sets out to save her mother.

Lovato’s song is the lead single on the soundtrack, which also includes cuts by Zedd, Colbie Caillat, AFI and Jessie J.

“Heart By Heart”” and Caillat’s “When The Darkness Comes,” were recorded specifically for the movie. Republic records will release the soundtrack on Aug. 20, ahead of the movie’s Friday, August 21 release date.

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