Talk:This Day Aria, Part 1/@comment-86.97.5.159-20120719184414/@comment-74.233.16.66-20120727122249

"An aria in music was originally any expressive melody usually, but not always, performed by a singer. The term is now used almost exclusively to describe a self-contained piece for one voice usually with orchestral accompanyment." - Wikipedia's entry for Aria

Here, they did something clever with the definition for aria: two characters with one voice as one of them is a perfect imitation of the other.