I've developed the theory that when we are
enjoying a piece of music our brains may be responding, or playing
along by creating additional, contributory vibrations in the ear.
Jerry Allison from the Crickets said that it was not uncommon for people to
come up to them after a Buddy Holly show and compliment the boys on the
back-up vocals.
The problem was that nobody sang backup on those shows, they didn't even
have mics. There were of course backup vocals on the records.
Of greater relevance may be the whole MP3 thing. The folks who developed
it are said to have used the idea that our ears didn't hear everything in a
wav file. There is apparently a psychological component in there, too.
Some times MP3's will sound fine to me, other times the same MP3's sound
just lousy.
It gets weirder. MP3's generally sounded really fine to my ears. Then I
did a project where I encoded some CDs using M4a, also known as AAC
Advanced. It was developed by the same people who developed MP3. It was a
real revelation.
M4a sounds so vastly much better - to me - than MP3 and WMA now that I can
often tell which type of file I'm listening to in a couple of seconds, and
MP3 and WMA just bug the heck out of me quite often. M4a absolutely never
sounds lousy to me.
I have to wonder if eardrum shenanigans are part of the mix in this regard.
I have several engineer friends who have a rule: Eight hours max. Anything
that sounds lousy the next day but was recorded or mixed within the span of
an 8 hour session will be repaired at their expense. Any mistakes made
after 8 hours must be covered by the client. Those engineers universally
blame ear drum fatigue.
Here's a weird non-eardrum phenomenon I have encountered recently. I just
did 17 days of editing on a project. I could only work for 2.5 hour
lumps. After that mark the timings of all my edits sounded horrible - way
off. I have encountered this in the past, though not so frequently as
during these editing sessions, where it was a constant. I'd go away for
about 90 minutes, mainly just goofing off, napping, annoying my cats. I'd
then go back into my mixing space and, like magic, all my timings were
right and true. Then I'd have another 2.5 hours before it'd all blow up again.