Born in Kansas, Rankin moved to Japan in 1971. According to his history at Pure Records' Casey Rankin Site, in 1976 his band Short Hope became the "First All foriegn band in Japanese industry to record and tour domesticaly."
In 1983, Rankin became possibly the first foreigner to record a TV anime theme song (he was predated by at least Mary MacGregor ["Sayonara," from "Adieu Galaxy Express 999," 1981] and Dara Sedaka ["Hoshizora no Angel Queen," from "Queen Millennia," 1982] in recording anime songs, but those had been for movies) when he not only performed "Orguss" opening and ending themes "Hyouryuu ~Sky Hurricane~" and "Kokoro wa Gypsy," but also wrote their tunes (the lyrics were by Kouji Miura):
The moment I first heard it back in '83, "Kokoro wa Gypsy" copped a near-top spot on my all-time anime hit parade, and hasn't slipped since. Have happy memories of friends gathered in various living rooms back in the day, all singing along with it between third-gen-copy "Orguss" episodes on VHS tapes...*sigh*
Am sorry there never got to be more Casey Rankin songs in the genre...but am mighty grateful to him for the two we have.
Edit: More info is on his MySpace page.