Clara?

"Clara?" is a leitmotif composed by Murray Gold that serves as the theme for Clara Oswald and her echoes. First appearing in The Snowmen, the leitmotif is hinted at in Asylum of the Daleks, but first appears in its main form in The Bells of Saint John.

Clara's theme appears throughout her tenure during Series 7, 8 and 9, but also represents her character in episodes such as The Pilot, when Bill asks the Doctor how he would feel if someone wiped his memories.

The piece appears in-universe as "Clara", a piece composed by the Doctor in response to his loss of memories about Clara. He performs this on electric guitar for Clara in her TARDIS, at that time both disguised as a waitress and a café, respectively (TV: Hell Bent).