Debussy lived into the age of recording, but the primary documents of his playing are his Welte-Mignon piano rolls. The Welte-Mignon contraption was a mechanical "player" which you set before a regular piano. It differed from the familiar player piano in that it could reproduce not only dynamics but touch and pedal technique. Mahler also recorded some of his pieces in this way. The problem with these things is their extreme fussiness. There's a problem with getting them to play at the intended speeds. You don't know, for example, how fast or slow Debussy intended, say, "La cathedrale engloutie" simply by looking at the roll. Also, apparently Welte-Mignon players were fitted to the individual piano. However, Pierian has used the talents of an engineer, Kenneth Caswell, who has devoted decades to the innards of the player, and the results have won the imprimatur of Harold Schoenberg himself, formerly a severe critic of modern Welte-Mignon reproduction. That's good enough for me.
All that said, I consider this one of the ten most important releases in the history of recording, even though I don't know what the other nine would be. Debussy is one of the master composers of keyboard music, along with Scarlatti, Bach, Beethoven, Chopin, Brahms, Schumann, Liszt, Bartok, Ravel, and Prokofiev. So the recording is the equivalent of having Bach play the Goldbergs for you. Does Debussy differ from benchmark performances, like Gieseking? Not to take anything away from Gieseking, but, yes, he does. I can describe it as an extreme inwardness, as if the composer were communing with himself. The fingerwork isn't as sure as some, but the outstanding feature of the playing is its outstanding singing or, considering the composer's subtle temperament, humming. I can't imagine anybody interested in Debussy's piano music passing up this CD.
We also get Debussy's acoustic recordings as Mary Garden's accompanist in the Ariettes oubliees and in an extract from Pelleas. These to me have more problems than the rolls, mainly because the sound is so crude, but I make that judgment precisely because I have the rolls. Without Caswell's dedication, I'd have been extremely grateful for the acoustic recordings.