TOD
It was my uncle whose cast album of THE MUSIC MAN was the first I was ever aware of. I didn't really know what a musical was, but I loved the sound of it and would ask him to put it on when at their house. I don't know why he had it at that time because he wasn't a musical lover or theater-goer at all, to my knowledge. But he did have reason to be in NYC along with my dad a year or two later, and they took the opportunity to see the show - in standing room.
My mom and dad had seen SOUTH PACIFIC on an early trip to NYC after Martin and Pinza were out of it. They didn't get the album, but several years later after we saw the movie (which is what introduced me to what a musical actually was), I had to have a recording. The first SOUTH PACIFIC they brought home was a cheap no-name one from the grocery store or some such, but I spent hours in front of that thing getting the music into my head as best I could, always attempting to relive the magic.
Finally -- FINALLY -- they got a console stereo to replace the crappy little record player, joined the Columbia Record Club, and, in competition with my dad's Mitch Miller albums, I voted on the cast album of SOUTH PACIFIC to be in an early shipment. It's my guess that that was the first real cast album in the house.