Well RMD,several aspects & origins of this "curiosity" have been touched on in other threads,but let me sum it up A.Q.A.P. :D
The first origin would be my parents & grandparents records (and 8 tracks!)
Next would be after moving to Cali. in 1977 and finding an "oldies' station (then 1955 to 1969).
Another such station is here in Phoenix, "Kool FM" one of thevery first oldies stations in the counrty. Which I found back in 1980 and most likely have heard every song they have by now.
In 1983/84 I found American Top 40 (Radio) & Top 10 (TV) w/Casey Kasum (voice of Shaggy on Scooby Doo). He seemed to be a wealth of knowlegde!
In 1986,my mother bought me The Billboard Book of #1 Hits (1955-1985 up to "We Are The World"). This book gave me many stories of the #1 songs of the past then 30 years. Then there's the B. Book of top 40 hits which has every artist wh has ever had a hit that big! (I own a "number' of these songs,to put it lightly. )
Mostly though,music is part of my family backdrop.
Everyone either plays an instrument (I still want to learn piano) or just has good musical taste and a good ear for quality.
I was also a good history student and paid attention in school.
Once I learn it,it never leaves me.
So,in short,for music...I've read many books,listened to a lot of radio & records,watched waaaayy too much TV & more recently a lot of time logged on the net!