DESCRIPTION:
The flashing fingers of Asher Denburg perform his arrangement of "Death Waltz" at a Thanksgiving dinner party.

(The original piece is performed electronically, and can't actually be played by a human being who only has ten fingers...)

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Since posting this, I have learned that it's misnamed -- the original song comes from a Japanese game called
"The Embodiment of Scarlet Devil" in the Touhou Koumakyou series.

The proper title is "U.N Owen Was Her?" (U.N.オーエンは彼女なのか？) It's the theme of the Extra-Stage Boss, Flandre Scarlet. As a result, the song's name could also be referred to as "Flandre's Theme".