Madame Butterfly

Madame Butterfly, known as Madama Butterfly in the original Italian, was an opera by Giacomo Puccini.

Grace Holloway was attending a performance of Madame Butterfly when she was called upon to perform cardiac surgery on the Doctor. She had a CD of the opera playing in the surgery, which the Doctor recognised as he fought the effects of the anaesthesia. The surgery forced the Doctor to regenerate. After regenerating and suffering from amnesia, the new Doctor found himself humming the aria which had played during his death. Later, in Grace's home, the CD itself jogged the Doctor's memory of being with Puccini before the latter had died. (DW: Doctor Who)

Some time before the events leading to his seventh regeneration, the Doctor found himself trapped in a decompressing airlock as the ship's computer played Danika Meanwhile's favourite track from Madame Butterfly. The music made the Doctor even more determined to get the door open and save himself, as he refused to die to the sound of what he'd dismissively called "elevator music." (BFA: The Death Collectors)