WSDM, Chicago was a prehistoric album rock (of the day) format, with jazz overtones. In it's heyday in the mid-60's It played album cuts from the Billboard album chart, which included Dave Brubeck Ray Charles, Ray Conniff and Sy Zentner. It was a forerunner of today's "smooth jazz."
It was a very well programmed and imaged station. I listened every day It helped race my teenage hormones.
The jocks were ladies known as "den pals" all 24 years old and under. SDM="Smack dab in the middle; The station with the girls and all that jazz."