"Southern Gospel Music" from Wikipedia:

The date of Southern Gospel's establishment as a distinct genre is generally considered to be 1910, the year the first professional quartet was formed for the purpose of selling songbooks for the James D. Vaughan Music Publishing Company. Nonetheless the style of the music itself had existed for at least 35 years prior although the traditional wisdom that Southern Gospel music was "invented" in the 1870s by circuit preacher Everett Beverly is spurious. The existence of the genre prior to 1910 is evident in the work of Charles Davis Tillman (1861–1943), who popularized "The Old Time Religion", wrote "Life's Railway to Heaven" and published 22 songbooks.

Southern Gospel is sometimes called "quartet music" by fans because of the originally all-male, tenor-lead-baritone-bass quartet make-up. Early quartets were typically either a cappella or accompanied only by piano or guitar, and in some cases a piano and banjo. Over time, full bands were added and even later, pre-record accompaniments were introduced.

Some of the genre's roots can be found in the publishing work and "normal schools" of Aldine S. Kieffer and Ephraim Ruebush. Southern Gospel was promoted by traveling singing school teachers, quartets, and shape note music publishing companies such as the A. J. Showalter Company (1879) and the Stamps-Baxter Music and Printing Company. Over time, Southern Gospel came to be an eclectic musical form with groups singing black gospel-influenced songs, traditional hymns, a capella (jazz-style singing with no instruments) songs, country gospel, bluegrass, and "convention songs" (which were more difficult). Because it grew out of the musical traditions of rural white people in the South, it is sometimes called "white gospel", to differentiate it from black gospel.

Convention songs typically have contrasting homophonic and contrapuntal sections. In the homophonic sections, the four parts sing the same words and rhythms. In the contrapuntal sections, each group member has a unique lyric and rhythm. These songs are called "convention songs" because various conventions were organized across the United States for the purpose of getting together regularly and singing songs in this style. Convention songs were employed by training centers like the Stamps-Baxter School Of Music as a way to teach quartet members how to concentrate on singing their own part. Examples of convention songs include "Heavenly Parade," "I'm Living In Canaan Now," "Give the World a Smile," and "Heaven's Jubilee."

In the first decades of the twentieth century, Southern Gospel drew much of its creative energy from the Holiness movement churches that arose throughout the south. Early gospel artists such as Smith's Sacred Singers, The Speer Family, The Stamps Quartet, The Blackwood Family, and The Lefevre Trio achieved wide popularity through their recordings and radio performances in the 1920s, 1930s, 1940s and 1950s. On October 20, 1927, The Stamps Quartet recorded its early hit "Give The World A Smile" for Victor, which become the Quartet's theme song. The Stamps Quartet was heard on the radio throughout Texas and the South.

Others such as Homer Rodeheaver and the Cathedral Quartet became well-known through their association with popular evangelists such as Billy Sunday and Rex Humbard.