Sometimes I wonder how natural sounding can be quantified. I play and tune my own piano so I know what a natural piano sounds like. But my perception of natural is from a performer's perspective, not a listener's perspective. Sound decays over distance so the perception of natural will differ for the listener. Some like the sound to simulate the feel of attending a performance but some like to be in the performance as if they're one of the performers. Personally I prefer the latter which tends to favor a thinner and more neutral sound.