The Abduction from the Seraglio

The overture to  was playing in Madame Karabraxos' vault at the time that solar flares overwhelmed the Bank of Karabraxos. The Twelfth Doctor, Clara, Saibra and Psi heard at least a few measures when they broke into that vault. (TV: Time Heist)

Behind the scenes
The piece is not named, except by the Red Bee Media subtitles for BBC One/BBC iPlayer. However, enough of the piece is played high enough in the sound mix that its nature is completely obvious to anyone familiar with Mozart's oeuvre.