counterpoint

Short definition from Wiktionary

Noun

1. 1
   A melody added to an existing one, especially one added to provide harmony whilst each retains its simultaneous identity; a composition consisting of such contrapuntal melodies.
2. 2
   Any similar contrasting element in a work of art.
3. 3
   An opposite point.
4. 4
   Obsolete form of counterpane.

Verb

1. 1
   To compose or arrange such music.
2. 2
   To serve as an opposing point against.