The creation, performance, significance, and even the definition of music
 
vary according to culture and social context. Music ranges from strictly
 
organized compositions (and their recreation in performance), through
 
improvisational music to aleatoric forms. Music can be divided into
 
genres and subgenres, although the dividing lines and relationships
 
between music genres are often subtle, sometimes open to individual
 
interpretation, and occasionally controversial. Within "the arts", music
 
may be classified as a performing art, a fine art, and auditory art.

To many people in many cultures music is an important part of their
 
way of life. Greek philosophers and ancient Indian philosophers

defined music as tones ordered horizontally as melodies and vertically

as harmonies. Common sayings such as "the harmony of the spheres

" and "it is music to my ears" point to the notion that music is often

ordered and pleasant to listen to. However, 20th-century composer
 
John Cage thought that any sound can be music, saying, for example,

"There is no noise, only sound."According to musicologist Jean

Jacques Nattiez, "the border between music and noise is always

culturally defined—which implies that, even within a single society,
 
this border does not always pass through the same place; in short,

there is rarely a consensus.... By all accounts there is no single and

intercultural universal concept defining what music might be, except
 
that it is 'sound through time'."