Turret Opera

The Turret Opera is an event in the single-player campaign of Portal 2 in which a group of Sentry Turrets form a unique melody via the movement sounds of their weaponry casings.

The opera is introduced as an easter egg in Test Chamber 16 of GLaDOS' testing tracks in Chapter 3: The Return, hidden beside a wall with a gap near the start of the chamber, where a Turret can be seen inside it. Upon entering, Chell would be able to witness various Turrets beneath the room as they serenade to the Prima Donna Turret.



Production
The song itself was produced by Valve composer Mike Morasky and vocalized by the voice of GLaDOS and the turrets, Ellen McLain, though the librettist is unknown. It was added to the Portal 2: Songs to Test By and the Portal 2: Songs to Test By (Collector's Edition) albums, the latter of which is available on Spotify and is accredited to Aperture Science Psychoacoustic Laboratories. The albums both act as the official soundtrack for Portal 2, with the Collector's Edition adding in songs from the series' first installation and even an audible mini-comic, among others. It was revealed by McLain that she "made up the words out of [her] bad Italian [...] on the spot."

Trivia

 * The lyrics can otherwise be read here in both its original and translated form on the popular lyric-recording and speculation site, Genius.
 * The word "Ciel" in the lyrics is speculated to be a play on words; it is pronounced almost the same as Chell. Despite the song being an Italian aria, "Ciel" itself can be translated from French to mean 'sky,' but in some specific and appropriate cases, 'heaven.'
 * Before becoming a voice actress, Ellen McLain was an opera singer.
 * In Portal 2, Weighted Companion Cubes can be heard humming it when nearby.
 * Before becoming a voice actress, Ellen McLain was an opera singer.
 * In Portal 2, Weighted Companion Cubes can be heard humming it when nearby.

Sheet Music
Sebastian Wolff has transcribed the song and provided free sheet music:
 * Sheet music for choir (SATB)
 * Sheet music for solo piano