"Soley, Soley"
From Tardis Wiki, the free Doctor Who reference
"Soley, Soley" was an "ancient" song that Suzie Costello's mother used to sing to her during her childhood. She told this to Gwen Cooper when it played on Gwen's car radio on their way to Greenleaves Hospital. Gwen had never heard it before. (TV: They Keep Killing Suzie)
Behind the scenes
The song was written by the band Middle of the Road in 1971, probably sometime around Suzie's birth.