In addition to performing, Ellis will host the broadcast, which will also feature Jonathan Ansell and Brian May, along with the BBC Concert Orchestra, conducted by Steve Sidwell.
The concert will feature music from such shows as Love Never Dies, Cabaret, Wicked, We Will Rock You, and My Fair Lady.
Ellis' stage credits include Oliver! and We Will Rock You in the West End, along with both the London and New York productions of Wicked. In addition, she was featured in the Chess in Concert performance.
Karimloo's credits include The Phantom of the Opera, Love Never Dies, and Les Miserables. He can be seen as The Phantom in the DVD and PBS broadcast of The Phantom of the Opera at the Royal Albert Hall. His debut, self-titled solo recording is set for an April 9 release.