Clara (song)

"Clara" was an instrumental song composed by the Twelfth Doctor. He performed the song several times for Clara Oswald in her TARDIS, disguised as an American diner, during a visit to Nevada. This occurred after he erased most memories of his former companion, so he was unaware that he was playing it for Clara herself.

The Doctor didn't know the origin of the tune. However, after discussing the fact that the Doctor no longer had specific memories of Clara, and in particular had forgotten a private message she gave him while in the cloisters on Gallifrey, Clara suggested that songs, such as this one, might represent those lost memories. The Doctor considered this and continued to play the song as Clara's TARDIS dematerialized around him. (TV: Hell Bent)

Behind the scenes
In reality, "Clara" was composed by series music composer Murray Gold. It is a very rare case of a soundtrack composition becoming diegetic.

Originally titled "Clara?" and also known as "The Impossible Girl" (the title it was performed under during the Doctor Who at the Proms (2013) concert and the Doctor Who Symphonic Spectacular), the composition was first heard on the soundtrack to TV: The Snowmen in 2012, most notably during the sequence in which Clara Oswin Oswald ascends to where the Doctor's TARDIS is hidden.

Prior to this, Gold had composed "Oswin Oswald", a musical theme for the character of the same name who appeared in TV: Asylum of the Daleks. This tune had a similar melody, but a number of noticable differences to the later track.

"Clara?", although introduced for Clara Oswin Oswald, became the recurring leitmotif for Clara Oswald proper, beginning with TV: The Bells of Saint John and was featured prominently in the opening minutes of the 50th anniversary special, TV: The Day of the Doctor.

It continued to be a recurring theme for Clara during Series 8 and 9, before becoming part of the narrative in Hell Bent; a sombre variant was featured during her death scene in TV: Face the Raven. Besides being played on camera during Hell Bent in an electric guitar version by Peter Capaldi, the tune also was prominently featured in the Cloisters sequence where the camera pans away from the Doctor and Clara during their private moment.

This is not the first piece of music attributed (in the fictional universe) to the Doctor; he previously conducted a fourth wall-breaking orchestral performance of another piece of music he created (TV: Music of the Spheres).