You mean you haven't heard? Its flawed, they discovered an error! Seven octaves up would be 128 times the frequency (2 ^ 7) but twelve fifths (12 fifths = 7 octaves) is (3/2)^12 = 1.5 ^ 12 = 129.746!! So twelve fifths are not really seven octaves! Its even worse for higher harmonics. So when pianos are tuned, either they are not exactly equal, or not exactly harmonic, or both!
By the way, can you guess the what the frequency span of seven octaves is, on a standard grand piano? (hint: it isn't 1 : 128 ).