[1][2][3] Hammack flourished in a wide spectrum of genres that included dixieland, Blues, swing, sweet dance music (e.g., Lawrence Welk), easy listening, gospel, liturgical jazz, musical theatre, Tin Pan Alley, classical, and film score.
Hammack also worked as a freelance arranger and writer for Bob Crosby, Lawrence Welk, and Tony Osborne.
His version of Raymond Scott's Powerhouse is featured on several space age pop compilations, and he also recorded with Esquivel.
Hammack earned a Bachelor of Fine Arts degree, majoring in music, from the University of Texas at Austin in 1945.
He had entered as a freshman in the fall 1938, but, beginning September 21, 1942, spent two years in the Air Force, stationed at Muskogee, Oklahoma.