Killen was promoted to executive vice president of Tree Publishing, where he worked with Roger Miller, Dottie West, and Dolly Parton.
In 1964 Killen formed the Dial Records label in order to promote Joe Tex, with a string of successful songs beginning with "Hold What You've Got" (1964).
Killen's work as a record producer included artists such as Louise Mandrell, Exile, Ronnie McDowell, Diana Trask, and T. G.
During this time, Killen worked with artists such as Faith Hill, Trace Adkins, Kenny Chesney, Reba McEntire and Bill Anderson.
In the mid-2000s, Killen's company worked with Outkast, publishing songs on the companion album to their 2006 film Idlewild.