The box set version of Cream’ “I Feel Free” in mono off Fresh Cream (‘66) sounds amazingly better than the stereo mix, which has some weird instrument placement going on….all the drums out of one channel, etc.
It’s well known that musicians (Beatles, etc.) in the 60’s would personally be there when the mono mixes were being done and then go home, leaving the stereo mix to whoever was left in the studio.
AM radio, mono only, ruled the airwaves then.