Hey, you know what-
This cat is aggressively affectionate. She's there because she is about to jump on my lap and throw her front paws on my shoulder to force me to hold her. She does it all the time. This time was different.
I had it a little loud, so it could just been that (but it was just as loud where she was)...
...but when she got in my lap, about to do her usual "paws on the shoulder, trick dad to hold me" trick - instead, she was suddenly distracted, and her head turned towards the mirror, and I saw her look back and forth a little.
Then she did turn to me and grab my shoulder like she usually did without hesitation.
I really wonder if she suddenly jumped into that audible illusion, the sweet spot that I'd been setting up - her head sure spun around like "Holy cow, something is there! But... I"m not seeing it! Where is it? Oh well - hug."
So maybe that's actually also a good sign.
I also tested this with my Fiancee, who - oh my god - couldn't be more of a polar opposite to me. I often avoid listening to music pretty much anywhere because the experience will be disappointing, where she's always got her phone out listening to music on the damn awful tiny tinny speaker (despite our having plenty of good, decent sized bluetooth speakers around). So I stuck her in front of it with a Madonna track that was imaging pretty good - I mean these are 3" speakers with tweeters so it's hardly a life-changing experience, but I asked her to tell me where she was hearing the image center, the stage width, the stage depth... and she gave all the right answers, pretty much the same as my observations...
...momentarily encouraging...
...then stood up and said "I don't care about any of that. I just want to hear the music."