For the music to "", O'Donnell began work on crafting the game's themes before Salvatori joined the team in February 2009. "Marty [O'Donnell] had started writing before me, and sent me some of his ideas," Salvatori said. "I picked a few that I felt I could add some magic to, and worked on those. I also came up with several ideas that I sent to Marty that he put his hands on." Once the duo felt they had enough material, the Chicago-based Salvatori flew to Bungie in Seattle to complete the arrangements and record live musicians.