Led Zeppelin II - not long after, I had a cassette recorder, so my album 'masters' never wore out!
But I remember listening with headphones, and not just playing through the album, but playing a song over and over - first listening to the whole song overall, then focus on the guitar, and then the bass, and then the drums. And then listen again, focusing on how the bass and drums interacted, and again how guitar and bass interacted, etc, through every combination (good thing they were only a quartet, with occasional organ and guitar over-dubs - that goes exponential!).
I'd say I not only know the words to every song, but every note of every instrument and drum beat and note bend and vocal growl of every song! I can 'sing along' with every solo, w/o a doubt. You just don't want to be in the same room when I do!
Hah, in fact - just the other day I was going through some old jazz and blues videos on youtube, inspired by a book I'm reading about New Orleans music history, and I came across references to early songs with some of the 'Lemon Song' lyrics. Well, I just had to hear "The Lemon Song" again, it's kinda easy to dismiss it a bit as a novelty for those lyrics - but I was immediately reminded of what a masterpiece this is. Every single time I hear it, I am blown away by the part where they go from the double-time back to single time, not in a jump, but they all slow down together over the course of one measure, and just drop back in perfect time to the original beat. I always picture them leaning into it like someone put the brakes on to slow them down! And that gong filling out the guitar sound on the first measure. Just incredible!
dah-dah dah-dah dah-dah dah da DAH, da DAH
"I should'a quit you babe...." 
-ERD50
