One thing often overlooked with those oldie classics is the simplicity. Very few if any efx, clear bass, soft drums, crisp guitars, vocals as the main feature, horns and strings to highlight or accent certain parts. Back "in the day" people were recording songs, not so much individual parts to be cut up and assembled later. Many of the songs were recorded in a fashion so they could be played live, exactly like the record. They had to keep it simple, many of those bands toured with only as much gear as they could haul in a Buick station wagon.