Most material released in the 50s and sixties was mixed with assumption that listeners would be listening to AM radio in their cars or a transistor radio. Most of the pop from this era actually doesn’t sound right to me when it is played back on a good system
Quality of recording
Sparked by @jumia 's post about the quality of recording...
I wonder how often recording engineers tweak recordings to sound best on the kind of system they think most of their listeners will have, as opposed to going for "pure" audio quality.