scott_w
I, too, bought the bulk of my CDs during the 80's. Most (99%) of these discs are flat transfers from the LP sources. Very little remixing, futzing with the original material going on there. The 1st real wave of re-mastering, remixing (not always revealed to the consumer), occurred in 1994.
Another big over-haul or 2nd wave of re-mastering/remixing occurred in 2000 to correlate with the HDCD codec.
Later on during the 2000's as pro-tools came online and 2010 forward with auto-tune, most of these discs are not flat transfers.
Happy Listening!