Okay, here was my evolution...
1960's: Even as a little boy, I was fascinated by radio. The radio always seemed to be on and I can remember songs from groups like the Young Rascals and the Turtles even before I entered grade school.
Early 1970s: I saw A Hard Day's Night on TV at age eight and instantly became a Beatles fan. Later the son of my my Mom's best friend, who was a few years older than me, would play albums by Deep Purple, Jethro Tull, Alice Cooper, etc. Meanwhile, I'm beginning to like groups like the Raspberries and Mott the Hoople.
1973: Bought my first record albums; The Mamas and the Papas 20 Golden hits and The Early Beatles. I'm now eleven years old.
Mid 70s : Began saving my lunch money and started buying all the Beatles albums on Apple reissues. In between, I also bought Out of Our Heads by the Rolling Stones. Probably should have bought England's Newest Hitmakers instead. I also bought the Kinks' Kinkdom during this period.
1976-1977: We were living with Mom's best friend and I'm sharing the basement with her oldest son. He's the one that gets me into Bowie with The Man Who Sold the World
Late 70's: My teenage years and I'm the only person at school who's actually into New Wave. I'm into Costello especially during this period.
1979-1981: My record store period and about the time I became a serious record collector. I shop at a local record store where I'll work at later. It's there that I discover garage rock through the Pebbles' series. I'm also collecting all sorts of psychedelic music as well as British punk bands like The Clash, Jam, and Sex Pistols. Also discover garage groups like the Thirteenth Floor Elevators and the Seeds.
1980s: I continue to collect records like they're baseball cards. Now my tastes have expanded into college rock led by REM and Aztec Camera. I'm also into the Eurythmics, Smiths, and Midnight Oil. Meanwhile I also buy a good chunk of my former boss' record collection.
Late 80s: My first CDs as I convert my Beatles and Bowie collections though I keep the LPs.
1990s: The WHFS years (first half anyway): Still continuing to look for vintage albums and frequent a monthly record show where I pick up catalogues of groups like XTC and Talking Heads. New music that interests me includes Nirvana, PJ Harvey, and Radiohead.
2000s: Only sporadically into file sharing. Convert record collection into Mp3s and forced to sell LPs at a record show for economic reasons. Also discover the indie rock scene and into groups/artists like Wilco, the Flaming Lips, and Sparklehorse, also Elliott Smith.
Today: Still searching for music by way of YouTube and music subscription sites like Mog and now Spotify. If I can get my Mp3 maker to work again, I'll be able to expand my collection much like I did when I was using Mog.
Well, that was long
EDIT: I missed that I also really got into Folk and Blues during the 90s.