I recently observed an interesting technique being used to radically alter the perception of synthesized sounds, by using the Pianoteq piano simulator, turning off all of the string and core piano sounds, and leaving only the level and key noise samples playing, then layering this on top of a synth sound - it had the amazing effect of making the synthesizer patch sound very realistic, as it added key noises and environmental (striker) noises to the background .. it was quite astonishing how this radically effected the perception.