Originally Posted By: Planobilly
I also know little about Claude Debussy. Did he use equal-temperament tuning?

Yikes, I hadn't thought to question that, I think equal temperament was pretty much the law of the land by then but I can't say for sure. He did write for whole tone scales, which suggests a presumption of equal temperament, but I don't know. And the question is totally relevant to explaining his choice of key.

Of course, we listen to his music in equal temperament and presumably ChatSonic's comment about Db is intended to apply to our listening experience today.