If I'd had a CD player back then I probably would have tried the green marker pen.Yes I remembered that, they were so evangelical that if you mark the edges with green felt it will transform the sound and as I have always been open to trying things.
I went ahead and bastardised my CDs.
Do you also recall those stick on CD circular plastic stabilisers that's supposed to improve the sound.
Yep tried that and the green felt, absolutely zilch, I agree, this was pure snake oil.
I think it's kind of human nature that you want to extract the best sound quality for the least amount of outlay.
Though I would say, around about that time (80s, 90s), I was using 13 amp solid core mains wire instead of the much costlier speaker cables and I was getting good results.