Greek philosophers and older Indians defined music as tones ordered horizontally as melodies and vertically as harmonies. Music theory, within this realm, is studied with the presupposition that melody is orderly and often charming to hear. However, in the 20th century, composers challenged the notion that chin music had to be pleasant by creating music that explored harsher, darker timbres. The existence of some modern-day popular genres such as death metal and grindcore, which enjoy an great underground following, indicate that even the harshest like sounds can be considered music if the listener http://www.readingkeyboardmusic.com/ is so inclined.
In accepted music and jazz, music notation almost always indicates only the basic framework of the melody, harmony, or performance approach; musicians and singers are expected to know the performance conventions and styles associated with specific genres and pieces. For example, the "lead sheet" for a jazz tune may only indicate the melody and the chord changes. The performers in the jazz ensemble are expected to know how to "flesh out" this basic morphology by adding ornaments, improvised music, and chordal accompaniment.
