Recently had a glaring example of this when I sent my amp away for extensive modifications/rebuild and pulled out my slightly modded Adcom 555 back-up amp. Gave it a couple weeks to come to life but never happened. What I wasn't hearing was any note decay, any hall sound. The notes played but that was it. Dynamically, it was like going from a Bosendorfer to a garden variety harpsichord. No ebb and flow to the music! No "life". Or you could call it a lack of "soul".