Jacox grew up singing with his big brother's gospel group the Sons of Jonas. At age 8, Martin's older brothers Jonas and Martell would take Martin around town to every church they could to sing. Martin made a name for himself with the help of his older brothers. Martin sang in churches in and around Brownsville, Tennessee, eventually catching the eye of Soul Stirrers founder J. J. Farley. Jacox joined the Soul Stirrers in 1966 and spent several years as their lead singer.