Hillsong UNITED's song "Oceans" off of their album Zion was the #1 Christian song of 2014, and still clings to the tops of the charts after 88 weeks. Now they have just released their followup album, Empires. They take care to present the image of a rotating cast of worship team members that cycle in and out of focus when called upon. But just who are the individual voices "Oceans," "Touch the Sky,", and "Captain"? With a new documentary film about the band being released in September of this year, now seemed like a good time to find out.

Joel Houston: The band's longtime "front-man" is the son of Hillsong Australia pastors Brian and Bobbie Houston. In addition to being a vocalist, guitarist and keyboard player in Hillsong UNITED, Joel Houston is one of the lead pastors of Hillsong Church, NYC. It is Joel Houston's gentle, melody-driven voice that listeners hear on Hillsong UNITED worship signatures like "The Stand," "From the Inside Out," "With Everything," and "Salvation is Here." His voice is also heard on their new track "Prince of Peace." As if all of that wasn't enough, Joel is also the Creative Director of Hillsong Church. Like most Hillsong UNITED members, he can be found posting snapshots of his life frequently on his Instagram account.

Jad Gillies: Jad Gillies is a worship leader and creative pastor at Hillsong Sydney. His is a voice with depth, as he takes a mellow tone at times ("Love is War") and breaks out in powerhouse potential at others ("Nothing Like Your Love"). Full name Jadwin Gillies, Jad lives in Sydney with his wife and two children. In addition to providing vocals and writing songs for UNITED, Jad also has video production talent, having been the producer of the long-form video "Live in Miami," which won a Dove award.

Matt Crocker: The vocalist featured on "Relentless," "I Surrender," "Heartbeats," and "King of Heaven," Matt "Matty" Crocker has a rousing energy and up-tempo insistence on songs which feature his singing. The worship experience with Crocker at the helm is at times both intimate and ecstatic, which UNITED recognizes by featuring his voice on some of their most vulnerable lyrics. Matt has been writing songs since he was a teenager growing up in Sydney.

Taya Smith: The newest addition to the band, Taya has said that she sees her bandmates as "older brothers -- whether they like it or not." Understatedly stylish with her curly cropped hair and bright lipstick, she describes herself often as "just a country girl," from Lismore, Australia and seems consistently humbled to now be leading worship for hundreds of thousands of people per year. Having taken over the role of female lead singer with the departure of Brooke Fraser in 2013, Smith was not present for the entire recording process of the Zion record. Her main contribution to that album also happened to be the breakout, record-setting hit song "Oceans." She made a statement about that song on her personal Facebook page: "Since 2013, I have had the honour and privilege to travel with Hillsong UNITED, singing 'Oceans' and it has become much more than just a song. As we have sung it again and again, it's been a defining opportunity for a country girl. It is a reminder of how I need to be living my life; stepping out and believing that regardless of any uncertain future or current circumstances, faith in God has no borders and I need to trust Him completely."

With the release of Empires, Taya features on a considerable amount of new tracks, including "Touch the Sky," "Say the Word," and "Captain." She gives songs a delicate and ethereal feel, the words delivered softly and with fervor. When she sings, it is as if Smith is in the midst of a prayer session in her own bedroom that we just happen to be privy to.

Other singers, songwriters and musicians featured on Empires include UNITED mainstay Jonathon "JD" Douglass, in addition to Dylan George Thomas, Simon Kobler, Benjamin Tennikoff, Timon Klein, and Michael Guy Chislett.

'Let Hope Rise', a film about Hillsong UNITED, is scheduled to be released September 30, 2015.