In second-species counterpoint, the counterpoint line moves in half notes against a cantus firmus in whole notes. This 2:1 rhythmic ratio leads to two new “fundamental musical problems” – one metric and one harmonic:
The introduction of harmonic dissonance into second species adds to the variety of the musical texture. However, it brings a tension that must be balanced with consonance to promote tonal fusion, and it requires careful attention in order to maintain smoothness in and out of the dissonance.
If we consider first-species counterpart the most “basic” interaction between two melodies, adding this second note against a harmony also provides an opportunity to begin discussing the shapes and patterns that composers use to embellish a simple melody.