<Tr> <Td> "</Td> <Td> Explaining what the heck took us so long is too complicated to go into here . There are a lot of reasons--I was busy telling other awesome stories at Seattle Grace, (...) I was raising my tiny human, my musical talent involves oboe - playing and nothing else, the network thought it was the dumbest idea they'd ever heard of and refused to do it . </Td> <Td>" </Td> </Tr> <P> The script was written by Rhimes in November 2010 . She centered the episode around Ramirez's character, Callie, and stated that the storyline would have developed regardless of whether it involved musical performances . Sara Ramirez used the opportunity to launch her career as a singer - songwriter; an alternate version of "The Story" is included on her debut EP, released four days prior to the episode's premiere . In this episode, Mark and Arizona improve their relationship . Capshaw said, "The traumatic circumstance leads to them having a greater understanding of each other and then appreciation, and then need for each other and desire to be in each other's lives . They come to care, I think, for one another ." </P> <P> Rhimes, executive producer Betsy Beers and director Tony Phelan selected songs that had become well - known by their use in Grey's Anatomy, and chose "the most iconic ones, the ones that best suited (their) singers, and the ones that made the most sense ." The multiple cover versions include the program's theme tune, "Cosy in the Rocket" by Psapp . The primary vocalists are cast members Ramirez, McKidd, Leigh and Chandra Wilson . The soundtrack also includes "How to Save a Life" by The Fray and "Running on Sunshine" by Jesus Jackson, performed as ensemble pieces by Ramirez, McKidd, Wilson, Leigh, Daniel Sunjata, Scott Foley, Ellen Pompeo, Justin Chambers, Raver, Dane, and Capshaw . Ramirez, McKidd and Wilson also perform together on Snow Patrol's "Chasing Cars ." Ramirez is the lead vocalist on "The Story" by Brandi Carlile, and "Grace" by Kate Havnevik, which also features the other female cast members, including Leigh and Sarah Drew on the chorus . Capshaw duets with Ramirez on KT Tunstall's "Universe & U ." Wilson is the lead vocalist on "Wait" by Get Set Go, McKidd on "How We Operate" by Gomez, and Leigh on Anna Nalick's "Breathe (2 AM)." </P> <P> Chyler Leigh's impressions on singing for the episode </P>

Who sings universe and u grey's anatomy