Madame Butterfly

Madame Butterfly, known as Madama Butterfly in the original Italian, was an opera by Giacomo Puccini. It was about a 19th century American soldier named Pinkerton whose poor behaviour led the the suicide of his geisha wife, the titular "Madame Butterfly". One song in the opera was Un bel di Vedremo, which Butterfly sang to her maid, Suzuki. Another song was Dormi amor mio, which Butterfly sang to her baby son Sorrow, which played while Grace Holloway operated on the Seventh Doctor. (PROSE: The Novel of the Film)

Grace Holloway was attending a performance of Madame Butterfly when she was called upon to perform cardiac surgery on the Seventh 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 Eighth 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. (TV: Doctor Who)

The Eighth Doctor later claimed that Madame Butterfly was such a perfect musical statement that it was simultaneously written on at least seven different worlds, the furthest from Earth being Larksup's World in the lesser Magellanic cloud. (PROSE: Beltempest)

Some time before the events leading to his seventh regeneration, the Seventh 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 angrily called "elevator music". (AUDIO: The Death Collectors) He also once heard it in a premonition while unconscious. (PROSE: Companion Piece)