The Blues is a vocal and instrumental form of music based on the use of the blue notes. It emerged as an accessible form of self-expression in African-American communities of the United States from spirituals, work songs, field hollers, shouts and chants, and rhymed simple narrative ballads.[1] The use of blue notes and the prominence of call-and-response patterns in the music and lyrics are indicative of African influence.

The blues influenced later American and Western popular music, as it became the roots of jazz, rhythm and blues, bluegrass and rock and roll. In the 1960s and 1970s, a hybrid form called blues rock developed from the combining of blues with various rock and roll forms.

http://en.wikipedia.org/wiki/Blues

Gospel music is music that is written to express either personal or a communal belief regarding Christian life, as well as (in terms of the varying music styles) to give a Christian alternative to mainstream secular music.

Like other forms of Christian music the creation, performance, significance, and even the definition of Gospel music varies according to culture and social context. Gospel music is composed and performed for many purposes, including aesthetic pleasure, religious or ceremonial purposes, and as an entertainment product for the marketplace. However, a common theme of most Gospel music is praise, worship or thanks to God, Christ, or the Holy Spirit.

http://en.wikipedia.org/wiki/Gospel_music

Bluegrass music is a form of American roots music, and is a sub-genre of country music. It has its own roots in Irish, Scottish and English traditional music. Bluegrass was inspired by the music of immigrants from the United Kingdom and Ireland (particularly the Scots-Irish immigrants in Appalachia), as well as jazz and blues. In bluegrass, as in jazz, each instrument takes a turn playing the melody and improvising around it, while the others perform accompaniment. This is in contrast to old-time music, in which all instruments play the melody together or one instrument carries the lead throughout while the others provide accompaniment. Traditional bluegrass is typically based around acoustic stringed instruments, such as mandolin, acoustic guitar, banjo, fiddle, and upright bass, with or without vocals.

http://en.wikipedia.org/wiki/Bluegrass_(music)

Singer-songwriter is a term that refers to performers who write, compose and sing their own material including lyrics and melodies. They often provide the sole accompaniment to an entire composition or song, typically using a guitar. The term is also sometimes used for a genre of music that is often performed in this manner. A number of other well-known musicians may write some of their own songs, but are usually referred to as singers instead.

http://en.wikipedia.org/wiki/Singer_Songwriter

Jazz is an American musical art form which originated in the beginning of the 20th century in African American communities in the Southern United States from a confluence of African and European music traditions. The style’s West African pedigree is evident in its use of blue notes, improvisation, polyrhythms, syncopation, and the swung note. more…

Old-time music is a form of North American folk music, with roots in the folk musics of many countries, including England, Scotland, Ireland and Africa. This musical form developed along with various North American folk dances, such as square dance, buck dance, and clogging. The genre also encompasses ballads and other types of folk songs. It is played on acoustic instruments, generally centering on a combination of fiddle and plucked string instruments (most often the guitar and, more generally in regions outside of the Northeast U.S. and Canada, banjo).

http://en.wikipedia.org/wiki/Old-time_music

Country music is a blend of popular musical forms originally found in the Southern United States and the Appalachian Mountains. It has roots in traditional folk music, Celtic music, gospel music, and old-time music and evolved rapidly in the 1920s. The term country music began to be used in the 1940s when the earlier term hillbilly music was deemed to be degrading, and the term was widely embraced in the 1970s, while country and Western has declined in use since that time, except in the United Kingdom and Ireland, where it is still commonly used in the United States. more…

The folk music revival is sometimes said to have begun with Pete Seeger. The Weavers, formed in 1947 by Seeger, had a big hit in 1949 with Lead Belly’s “Goodnight, Irene”. This hit was probably one of the first glimmerings of the folk music revival. more…

Americana
From Wikipedia, the free encyclopedia

Americana refers to artifacts of the culture of the United States. Examples of this culture include baseball, apple pie, jazz, Superman, the Diner, George Gershwin’s Rhapsody in Blue, the music of Aaron Copland (notably his Fanfare for the Common Man), and American folk art, such as that of Norman Rockwell. more…