Neptune was born in Oakland, California, on November 13, 1951 and moved with his family to San Diego, California when he was two. He played trumpet in high school and later was a drummer in a rock band. For college he chose the University of Hawaii, basically for surfing, but also began to study ethnomusicology. "I was interested in learning the Indian tabla," recalls John, "but at that time in Hawaii there was no one to teach me. My number two choice was the shakuhachi.