It's more important that the musicians are in tune with each than with concert tuning. Analog recording and manufacturing had numerous places where small errors in pitch could occur. The biggest selling jazz album of all time, "Kind Of Blue", had pitch/speed issues. I can imagine for someone with perfect pitch that it could be annoying, but for most it doesn't matter. With digital recordings you can intentionally pitch up or down to your heart's content. It's just another FX tool.
Why is so much music recorded out of key?
As a guitarist, I like to sometimes listen to music and figure out a solo or sometimes play along with a song. My guitar is in perfect tune but a lot of the time the music is off and in between 2 keys. Like a semi tone off key. This really never happens when listening to a live recording, only studio recordings. I assume all the musicians tune up during a session and of course piano is already tuned to a standard. So has anyone else noticed this and can explain why. Don’t try to blame it on my turntable as it happens with digital streams and cd releases as well. Been noticing this for years. What gives??