CW senior VP and creative executive Chris Donovan, decided that using the old spiritual "O Death" (heard in "Brother Where Art Thou") fit well with the themes of Season 5. He contacted Jennifer Titus, a well-known name around the CW, about singing the song. She recorded a preview of the song on her iPhone and sent it to him.
Donovan was extremely impressed, and upon a slight re-write of the lyrics to fit the show better, Titus came into the studio and recorded the official version. CW Staff members recorded the humming heard in the song, and Leonard Richardson, the executive in charge of music on the CW, mixed the track.Source.
- For more information on Jennifer Titus, visit Jen Titus IMDB