What's the name of the piano piece played in the new Halo 3 commercial?!

Question:

What's the name of the piano piece played in the new Halo 3 commercial?

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The song has a classical sound...I would love to know the name of the song and the composer.

Answers: Frederic Chopin’s Prelude in D flat Major, Op. 28, No. 15, “Raindrop.”

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