I think it happens when an upgrade makes a significant difference in balancing the system. What you have posed has happened to me at least 8 times. After a while I find some diffeciency in the sound after months of listening and look for a specific upgrade to rectify the problem. I've been building a system for about 10 years. This effect happened to me when I first purchased Martin Logan's Monoliths. Then when I upgraded to Levinson amplifiers. Again when I upgraded to a VPI TNT turntable. Yet again when I upgraded to a 380s pre-amp. When I biamped the system using Krell mono's on the bottom it happened again. Each time the music became very "right". But after a while I tuned into problems that needed attention. I like many of the other posts listen to many different systems. In fact, much of my listening is on airplanes using ER-4s headphones and a headroom amplifier. I also listen quite a bit in my office (background), classical music on small B&Ws. I enjoy music, but I'm not always listening so intently to the technical and sonic attributes that a high end system is necessary. You can still get the attributes of the performance, if you allow yourself to do that and not be critical of the fact that a kettle drum will never sound like a kettle drum on bookshelf speakers (at least not mine). Lastly, you might be interested in whether or not persons play a musical instrument. It seems to be a trend that musicians have very poor sound systems. On possible explaination for this is the music is in their head and they do not need a high end system to re-create the emotional response. All they need is a brilliant performance. I'm not like this. I play the piano regularly, and thoroughly enjoy a system that can reproduce the piano extremely well. Since the piano has such a large range (frequency and dynamically) and has so many harmonics, paricularly when coupled to the room response it is very difficult to reproduce. Perhaps this is why I know that my system could still use improvement.
Musical threshold event
This thread is related to several others concerning being an Audiophile versus a music lover....but a shade different. From my own personnal experience and from conversations I've had with others, as a person is building their system, there seems to be a threshold beyond which the beauty of the music suddenly grabs your attention instead of the beauty of the sound. After that threshold is crossed, the music is front and center. Recordings are listened ALL the way thru and there is less pre-disposition to mess around with the equipment, perhaps, in part, out of fear of loosing the magic. For me this happened when I got a pair of Forte 4s to drive my Martin Logan Quests. The music grabbed my attention instead of the sound (which was also quite good). All of my equipment purchases past that point have been in pursuit of the musical experience. Sound quality matters, but compliments, instead of dominates my equipment selections. I'd like to know at what points all of you crossed that threshold and what combination of equipment got you there. Contrasting that threshold point for vinyl and digital would be neat too.