January 27th marks the 50th anniversary of the death of Mahalia Jackson, the world's greatest gospel singer, and the person who more than any other, helped spread gospel music internationally and paved the way for it to be accepted as part of American culture.

Blessed with a great voice, Mahalia was one of the first black artists in America during the 1940s and 50s who sang and made records which appealed to both black and white audiences.

Born in New Orleans on October 26, 1911, Mahalia started singing in church aged only four. After her mother died, her father sent her to live with an aunt in Chicago when she was 16. There she found work as a domestic helper, joined the Greater Salem Baptist Church and sang in the choir.

Soon Mahalia's unique voice was attracting attention, especially among the smaller black churches in Chicago. They invited her to sing at their services, conventions, and dedicated events. The larger, more formal churches however ignored her, as they didn't like her energetic and rhythmic style of singing. What they believed was that Mahalia was bringing the blues into the church, and they would have none of it.

Although brought up a devout Christian, Mahalia admired Bessie Smith and Ma Rainey - two female giants of the blues - but she never had any inclination to sing anything other than gospel music.

In 1937, Mahalia met Thomas Dorsey, the great gospel composer who coined the phrase 'gospel music,' and who wrote such classic hits as "Precious Lord", "It's a Highway to Heaven", and 'Peace in the Valley'. Mahalia worked with him for 14 years, accompanying him to gospel concerts and singing his songs while he sold the sheet music.

An entrepreneur at heart, Mahalia realised that she wouldn't make a living solely from her music and took a beauty course to provide an income for herself. She opened a beauty salon in Chicago, worked during the week and left the weekends to her music.

With Dorsey's songs and her inimitable style of singing, Mahalia began to attract the larger churches in Chicago to her music. Her reputation preceded her and in 1947, Apollo records approached her to make a record. In the same year, she released "Move on Up a Little Higher". It became a big international hit, selling eight million copies, and launched her as a gospel artist.

Now a household name, Mahalia performed to sell-out audiences in America. She appeared at the Carnegie Hall, was a guest on the Ed Sullivan show, hosted her own radio and television shows, and was featured in the film "Imitation of Life". She also toured Europe, was immensely popular in Norway and France, and made many memorable appearances there.

As a much in demand singer with a unique voice, Mahalia turned down many approaches to sing secular music. She refused lucrative offers to sing in nightclubs and to segregated audiences. She also refused to sing songs other than religious ones, nor would she sing in places she considered unsuitable and unfit for a gospel singer. Such was her uncompromising faith.

In 1963 Mahalia sang at the well-known 'March on Washington,' where King made his famous 'I Have a Dream' speech. We all remember what he said, or the famous part of it, but what is perhaps less known is the part Mahalia played in it.

Mahalia was like a warm-up act for King. He referred to her as 'a blessing' and would frequently ask her to sing before speaking.

They first met in May 1957 when Ralf Abernathy, the director of the Southern Christian Leadership Conference, asked her if she would lend her support to the Alabama bus boycott, the event that launched King, the civil rights movement, and Rosa Parks.

The meeting was a defining moment and as a result, Mahalia appeared many times with King and was frequently by his side. She was a trusted friend, confidant, staunch supporter of King and the civil rights movement, and financed many of its activities.

On that special day in August 1963, King was the last of the speakers to address the 250,000-strong crowd who had gathered at the Lincoln Memorial in support of the civil rights legislation going through Congress. Marian Anderson, Joan Baez, Peter, Paul and Mary, and Bob Dylan had all sung earlier, but before he spoke King called Mahalia and asked her if she would sing. In her incomparable style, Mahalia launched into the well-known spiritual, "I've Been Bucked, and I've Been Scorned".

With the crowd and the occasion 'sanctified', King began to deliver his speech. He took a while to warm to his theme and seemed to be wandering around the text. Seeing what was happening, Mahalia shouted in a 'call and response manner' so beloved by black church congregations, "Tell them about the dream Martin, tell them about the dream."

Mahalia had heard King use the refrain before and history tells us that on hearing her, King departed from his prepared text and launched extemporaneously in a towering Southern Baptist style into a new vision of America - an America "where every valley shall be exalted, every hill and mountain made low, the rough places made plain, the crooked places made straight, and the glory of the Lord shall be revealed, and all flesh shall see it together".

"And when this happens, and when we allow freedom to ring, when we let it ring from every village and every hamlet, from every state and every city, we will be able to speed up that day when all of God's children, black men and white men, Jews and Gentiles, Protestants and Catholics, will be able to join hands and sing in the words of the old Negro spiritual: Free at last. Free at last. Thank God almighty, we are free at last."

Within five years King was dead but Mahalia went on to have an incredible international career, selling millions of records and inspiring a generation of gospel artists. In 1972 she too died, and at her funeral a young Aretha Franklin sang "Precious Lord", the Dorsey classic. It was as if the baton of gospel music had safely passed on from one generation to the next.

Roy Francis is an award-winning former BBC 'Songs of Praise' producer and the author of 'Windrush and the Black Pentecostal Church in Britain'.