Label changes can create headaches not only for the artist but for the music buyer.  During Bowie's RCA years, there was ChangesOneBowie and ChangesTwoBowie.  When Ryko bought his back catalogue, (Space Oddity to Scary Monsters) a single Changesbowie CD, consisting of his old RCA singles and EMI singles came out in 1990, and this is what launched the discovery of old Bowie for me.