Music is a contested aesthetic evaluation of what constitutes music. Music is an art, entertainment, or other human activity which involves organized sound. It is an art form that involves organised sounds and silence. It is expressed in terms of pitch (which includes melody and harmony), rhythm (which includes tempo and meter), and the quality of sound (which includes timbre, articulation, dynamics, and texture).

Music may also involve generative forms in time through the construction of patterns and combinations of natural stimuli, principally sound. Music may be used for artistic or aesthetic, communicative, entertaining, ceremonial or religious purposes.It is an art form that involves organised sounds and silence.

It is expressed in terms of pitch (which includes melody and harmony), rhythm (which includes tempo and meter), and the quality of sound (which includes timbre, articulation, dynamics, and texture).

During the twentieth century, a crucial change in the history of folk music began. Folk material came to be adopted by talented performers, performed by them in concerts, and disseminated by recordings and broadcasting. In other words, a new genre of popular music had arisen. This genre was linked by nostalgia and imitation.to the original traditions of folk music as it was sung by ordinary people. However, as a popular genre it quickly evolved to be quite different from its original roots.

The rise of folk music as a popular genre began with performers whose own lives were rooted in the authentic folk tradition. Thus, for example, Woody Guthrie began by singing songs he remembered his mother singing to him as a child. Later, in the 1930s and 1940s, Guthrie collected folk music and also composed his own songs, as did Pete Seeger, who was the son of a professional musicologist.

Bluegrass as a style developed during the mid 1940s. Because of war rationing, recording was limited during this time, and the best that can be said is that bluegrass was played some time after World War II, but no earlier. As with anymusical genre, no one person can claim to have "invented" it.