Ask most people what the modern gospel choir sound is built from and they will describe the thing itself, the layered soprano, alto and tenor lines that seem to have always existed. They did not always exist. Before Dr. Mattie Moss Clark, most gospel choirs sang in unison or split into two loose parts. Clark, trained classically and installed as the Church of God in Christ's international minister of music by 1968, rebuilt the sound from the ground up, writing three distinct vocal lines into arrangement after arrangement until the technique became the industry standard it still is.
"Salvation Is Free" is one of the songs that carried her name past the choir stand. Her biographers describe her adding more than a hundred songs to the gospel repertory over her career, and this one is named, alongside "Save Hallelujah," among the small number that became standards, sung in churches that never learned her name and never knew the arrangement they were using came out of COGIC's own national music department.
That is worth sitting with. This was not a song written to represent the church to outsiders. It was written from inside the church's own machinery, by the woman running that machinery, for the choirs she was personally training in jurisdiction after jurisdiction. No composition date survives in the sources checked for this record, and none is invented here. What survives instead is the pattern of a career: an organization builds a national music department, appoints a director, and the songs that director writes for her own choirs end up sung by people who have never set foot in a COGIC sanctuary. That quiet migration from one church's internal repertoire into the wider vocabulary of American gospel music is Clark's whole legacy in miniature.