The four elements of melody, harmony, bass, and rhythm give the typical four dimensional textures to popular music. However, another element adds a level of interest and intrigue to the music. Between the lines of the melody or between verses is a secondary melodic line which functions as a complimentary melody to the main melody. When fitted between lines of the regular melody, it is most often shortened to just a few notes, rarely carries any words, and is much less memorable than the main melody.
It could be the trumpet player squeezing a musical idea in between the lines of the sax solo in jazz. It could be a steel guitar sliding a melodic thought while the country singer takes a breath at the end of the phrase. It could be a rock or blues keyboard player pushing a commentary between lines of a guitar solo. It could also be a group of backup singers doo-wahing behind the lead singer.
This musical example is built around a melody (trumpet), harmony (piano), bass (acoustic bass), and rhythm (brushes on drums):
When the counter-melody is introduced, you have a musical “conversation” between it and the melody. This musical example is exactly the same as before, but a counter-melody (saxophone) is introduced:
The countermelody brings variety to the musical product in that it provides a secondary melodic commentary on the emotion and feel of the song.
The counter or secondary melodic idea brings diversity to the musical product in that it is often played by an instrument which is in a complimentary timbre (or aural color) to the instrument or voice playing the main melody. In this way, the sound of the countermelody is set apart from the sound of the main melody; guitar/voice, harmonica/guitar, saxophone/voice, flute/guitar.
On occasion, the countermelody is introduced first in the section which sets up the song, called the introduction (see element on structure). Then it reoccurs throughout the song around and between lines of melody, and then may be reiterated again at the end of the piece.
Although the presence of a countermelody is not guaranteed, it is a frequent guest in many forms of popular music, including country, jazz, blues, rock, and pop.
When the five elements come together – melody, countermelody, harmony, bass, and rhythm – a cohesive and polished product is heard.