Brian Transeau, a producer, DJ and composer known to electronic music fans as BT, wrote a tribute song for his 3-year-old daughter, Kaia, on his last album.
"It's a very cliche thing," Transeau told ABC News, describing what his relatively new fatherhood has meant to him. "But it's the greatest satisfaction and impact on my life, above everything I've ever accomplished personally or professionally."
The popular artist's movie scores include "Monster" and "The Fast and the Furious" and he has collaborated with artists ranging from Britney Spears to David Bowie. But right now he's working intensively with private investigators and police to find the missing child.
Authorities in Maryland have a warrant for the arrest of Kaia's mother, Ashley Duffy. Police say the woman, who does not have custody of Kaia, broke the law when she took off with the child in December.
"There has been a warrant issued for her arrest," Melanie Hadley, a spokeswoman for the Montgomery County Police Department, told ABC News.
Duffy faces child detention and abduction charges, both tied to her alleged departure from the state. Hadley also confirmed that Transeau had obtained an emergency return order that prompted the court to issue the arrest warrants.
"It's an open investigation," Hadley said, but added that there were few details authorities could share.
Transeau says that he last saw his daughter, nicknamed "Kiki," Dec. 19, when he agreed to allow Duffy, whose residence is in Brooklyn, N.Y., to spend an overnight with the child at a hotel in Silver Springs, Md.
The musician described being surprised when his phone rang that night with the caller coming up as Duffy. Expecting to hear her voice, he found his daughter on the line, who he said told him that Duffy, 27, had hit her and that she was scared by her mother's behavior. He then had a conversation with Duffy, who he said cursed him out and said he was interfering with her relationship with the child.
Transeau has not been in custody of the girl since that night.
Transeau alleges that Duffy has been violent with him before. Police had been called to their house when they previously lived together in California, he said, but no charges were ever filed involving either of them. Duffy, however, had never hit their child, he added.
A spokesman for the Los Angeles County Police Department confirmed that police had responded to the artist's house on domestic assault reports, but said that neither Transeau nor Duffy was ever arrested. A spokesman for the Los Angeles County District Attorney's Office said that neither had ever been prosecuted for domestic assault charges.
The two were never married and had no formal custody arrangement in place when Duffy allegedly took off with the child, Transeau said. Because there was no custody arrangement, it took more than two weeks of legal work before arrest warrants could be obtained, which happened Jan. 5, according to police.
In the interim, he said, Duffy and Kaia were tracked to Brooklyn and reportedly were last seen in New York, Dec. 26. Transeau has not heard from Duffy or his daughter, and he said the few mutual friends Duffy has called say the woman would not disclose her location. Her cell phone goes straight to voice mail.