Greatest hits and other compilations.
I always loved a good greatest hits compilations and many of my early album purchases were collections such as Jimi Hendrix's
Smash Hits, The Four Seasons'
Golden Vaults and many Motown hits packages.
The Kink Kronicles, released in 1972, was a different kind of compilation and quickly became one of my favorite all time albums.
The Kinks had switched to a new record company and their old label released this album compiled by a group of rock journalists specifically for the American market. The album's unique perspective reflects it's creation and does not contain many of the early standard songs from their Greatest Hits album but does provide songs from 1966 to 1971 including some previously unreleased tracks.
I don't think there were many compilation albums released in the 60's and 70's that contained this kind of view of a artist or group using non-hits and unreleased material. That would happen later with the introduction of multiple disc box sets in the late 80's followed by the many deluxe reissue sets of the 90's and beyond. I got hooked then and now.
