Where do I find the turrets practicing singing in Portal 2?
I read in this question's answer that you can see the singing turrets of the Portal 2 ending practicing earlier in the game.
Where can I find them?
You can watch some of the turrets practicing their singing from a vent in Test Chamber 16:
You can see the soprano turret in the elevator after the first hard light bridge level — chamber 11 in chapter 3.
