Tangential, but I've had a somewhat similar experience. Iron Maiden's "Flash of the Blade" used to be my favorite song by the band, but somehow it was not one of their biggest hits. I had it recorded on tape and would listen to it daily. When I finally had money I bought the album it was in, and couldn't not believe how bland the song sounded. Turns out the cassette player I used to play the song was speeding it up - not super noticeable on its own, but obvious if you compared it directly, and the sped up version is MUCH better.