We are doing the Allegri Miserere in choir again this semester. I love that song so muchly. The soprano soloist's part goes up to that high C and oooooohhhhhh. (It's not so good in this version because you can hear her reaching, but when Kristen sings it it's like she was born to it)
It's like the soprano Air in Messiah - I think it was I know that my redeemer liveth - when the music only called for the soloist to go up to the E, but instead she floated up to the B, and it was like watching a blue butterfly land on a leafless branch and spread his wings before fluttering away again.