[2] He moved to Hollywood, California in his early 20s, and became a staff writer for United Artists Music Publishing.
His first credit was songwriter of "Ten to Eight" from Helen Reddy's 1975 album, No Way to Treat a Lady, which was also used as the B-side to her "Somewhere in the Night" 7-inch single.
[5] He performed "Ten to Eight" on the BBC music chart television program Top of the Pops on February 9, 1978.
In the film, Randy Quaid & John Hurt sing "Istanbul Blues," but on the soundtrack album, Castle performs it.
[10] Castle set up a recording studio in his home and focused more on composing and orchestrating music for commercials, television, and film.
He scored music for the following: Vicki!, The Jenny Jones Show, the HBO Rodney Dangerfield special Opening Night at Rodney's Place, the Hallmark Hall of Fame special Home Fires Burning (January 29, 1989), Chuck Workman's The Beats, the Star Trek: The Original Series video episode "The City on the Edge of Forever", a California Army National Guard promotional film entitled California the Beautiful, and an LAPD drunk-driving spot entitled It Could Happen (starring Teri Garr).
After a long battle with cancer, Castle died on May 8, 2019, in Los Angeles, California,[17] shortly after being moved into hospice care.