"Missy's Theme" is a leitmotif composed by Murray Gold. It accompanies the female incarnation of the Master portrayed by Michelle Gomez during series 8, 9, and 10 of Doctor Who.
The piece is mostly of synthesized, sounding dreamlike, evoking Missy's relation to the heaven-like Nethersphere in Series 8. It is led by the vocals of Halia Meguid, whose voice, although singing English lyrics, is heavily altered to sound like a hidden or reversed message fading in and out of the ethereal instrumental.
The piece first appears in The Caretaker when Seb welcomes CSO Matthew to the Nethersphere, and reappears in subsequent scenes involving Missy and the Nethersphere during Series 8, and also in Empress of Mars.
An ominous arrangement of the theme is also heard during Missy's meeting with Clara in The Magician's Apprentice, and another orchestral arrangement is later heard in The Lie of the Land.
Both the main version of "Missy's Theme" and an extended concert arrangement were included on the Series 8 soundtrack, along with other variations of the theme appearing in other tracks. The concert arrangement, although released on the Series 8 soundtrack, only made an appearance in an episode by Series 10's The Lie of the Land.
Original Lyrics
The vocals in the song were performed by Halia Meguid. The unaltered English lyrics can be found on Meguid's tumblr account, as well as a brief explanation as to the process of creating and altering the song. According to her description, Murray Gold wrote the lullaby for her to record a capella, and then he edited it for the final track heard.
Sing the days of love
Softly lay me down
Tenderly the night will come
In your sweet embrace
Sing the days of love
Softly lay me down
Tenderly the night will come
Gently lay me down