Music has always been an integral part of Christian worship since the foundation of the first churches. Much of this early Christian music was not intended for commoners to perform, however, since it was in the form of chants or musical liturgy during the Mass ceremony. When the Protestant movement gained popularity, the concept of composing hymns for congregational singing also became more accepted. When Europeans began to colonize America, many of them used these hymns during often lengthy worship services. This importation of sacred church music formed the basis of "white" gospel music, as composers used the musical styles of their times to create new hymns.
Meanwhile, the slave trade introduced native Africans to a foreign and often hostile land. Many of these slaves brought with them a rich tradition of spiritual songs, and they would use these songs to communicate or commiserate with others in the fields. Christian worship became a central part of the African-American community, and these spirituals formed the basis of their emotional and impassioned worship style. Negro spirituals provided a sense of comfort during times of hardship, and many of these songs were combined with secular musical genres such as the blues or ragtime to form the earliest "black" gospel music.
The two paths of gospel music appear to have collided in the South during the early 20th century. White country performers often exchanged musical ideas with their black counterparts, including the use of religious themes in secular music. White musicians were quite familiar with the harmonies and upbeat qualities of modern hymns, leading some to form vocal quartets backed by the instruments commonly found in country bands. This branch of gospel music, with white singers using many of the vocal techniques of their black counterparts, became known as Southern gospel.
While white performers were enjoying success in the Southern gospel music gospel, black gospel music performers were having a more difficult time finding a general audience for their music. Many black performers found it easier to break into secular musical genres such as boogie-woogie, jazz or blues than gospel music. Only a handful of black performers before the 1950s succeeded in bringing their form of black gospel music to a national audience. Early rock and roll performers such as Little Richard and Ray Charles did manage to incorporate the soulful sounds of black gospel music, but their music remained firmly in the secular realm.
Gospel music perhaps got its best introduction to the general public through the efforts of a young white singer named Elvis Presley. Presley had grown up listening to black gospel music, and had unsuccessfully auditioned for a Southern gospel quartet before finding success in the secular music world. Presley's rendition of a black spiritual called "Peace in the Valley" demonstrated that gospel music could be marketed to the general listening audience. Subsequent gospel music recordings by Ray Charles, Aretha Franklin, Elvis Presley and many other famous singers helped to establish gospel music as commercially viable.
By the 1970s, Southern gospel music had evolved into a more polished, modern sound. With the rise of alternative churches and youth-oriented worship centers, a form of modern gospel music called "Praise and Worship" also became very popular. Meanwhile, a number of black gospel music artists adapted a new style based on grittier urban sounds and a strong R&B influence. This subgenre is generally known as contemporary urban gospel music. source:http://www.wisegeek.com/what-is-gospel-music.htm