It's a pieced of art that symbolizes life. That's why it is associated with art more than any other media.
The correct answer is :
A second voice
Explanation:
As no genuine independent other voice exists, this is a form of heterophony. In its earliest stages, organum needed two musical voices: a Gregorian chant melody, and the same music transferred by a consonant interim, regularly a complete fifth or fourth.
A group of instruments or voices is a section