McElwain completed a B.Mus.Ed at Florida State University in 1958 and an M.Mus.Ed in 1959. She began teaching in the Jennings, Florida public school system. From 1962-1967, she taught piano, organ, and music classes at Monterey Bay Academy in California and, for two years, taught at Antillian Union College in Puerto Rico. She subsequently did additional graduate work at FSU, completing an M.Mus. in music therapy in 1974 and a Ph.D. in music education with an emphasis in music therapy in 1978.

McElwain has written several articles and books on the effects of music on the mind and body. Additionally, she has made a number of presentations on music therapy, including its use for the severely handicapped, for exceptional children, and literature for possible use in working with the deaf and blind. More recently, she has given lectures on the "Philosophy of Morals and Ethics of a Christian Music Therapist" and several Power of Music Seminars, presentations on the power of music in the spiritual experience.

Beginning in 1992, with the release of her first book, The Power of Music, McElwain has been a spokesman for the importance of choosing music carefully and thoughtfully. Her counsel, based on her experience as a music therapist, is summarized in her fourth and final book, The Lord is My Song. It is a revision and compilation of earlier writings and spoken presentations on the subject of music's influence on the moral, mental and physical aspects of life.

McElwain now resides in Kerens, West Virginia.