Do the Audio gods shine upon you?

Mes, even small letters couldn't diminish your post further, but it's a nice thought.

From a totally different perspective: Perhaps the differences are the beings in your proximity at the time?
This is WAY off in 'Twilight Zone' territory but listen up!
99.9 percent of use (me too) don't sense "the other realm" but that doesn't mean it can't exist (I only post this as a theory, not as my own belief system) If a dozen Devas decide to stop by and listen in with you... the joy they experience may extend into your perceptual world. (Devas are Hindu angels, sort of) I would think the experience would be VERY pleasant.
Or perhaps the ghost of Mozart may visit???? ha ha

Simply stated, "YES"! And, when it happens I take full advantage and play till I can't play no more. BTW, this happens to me when I play my guitar. Sometimes it sound better or I enjoy my playing more. It isn't so much the quality of my playing but rather where my head is at. I bet if you were consistantly hooked up to a MRI or CAT scan it would show diferances related to your perceptual enjoyment of the activity even when the enntertanment is repeated. I bet it comes down to some sort of organic variable with in our bodies. Sometimes it is the chicken and sometimes it is the egg. I bet the same could be said for the enjoyment of food. Why does that icecream in the icebox taste so good one day and average the next? Again, I think that at times the real magic happens when the organic variables are in just the right balance. Or maybe it just the AC.

Ramstl is right about the "organic variables", but also about the AC, which is generally better at night. The right kind of temperature und humidity has an effect, I have found and of course listening in the dark, which will let your subjective perception of soundstage bloom and deepen. But then also the company you share your music with will often have an effect. Sounds crazy, but I have had repeated system breakdowns when I wanted to show off to certain people, while with specific others, the mutual enjoyment of the system, led to a deeper and deeper involvement with the musical event. I generally have found, that shared listening with a person close to you, makes for a deeper enjoyment and involvement,compared to just listening by yourself.

You are not nuts, slowhand, nor are you apparently alone.
Recently I played both my Buena Vista Social Club and my
Snatana Supernatural CD's and even my wife commented from the other room that something was missing that had been there the last time we played them - like a day or two ago!
I checked all connections, speaker position, etc. But nothing had changed! Except the Audio gods had temporarily sucked back all the magic out of my system/recordings. As far as a rational explanation, power variances(I do not have a line conditioner or UPS hooked up on this system) could make a difference, as well as ambient humidity and room temperature. Right. I obviously offended various audio gods, like Detail, Imaging, Soundstaging, MacroDynamics,
and needed to do penance.
After that, I am just plain mystified.