Polyphonic music. Something in the lines of ‘opposing points’, like saying point against point. In the case of two voices, you can have a bass line as the cantus firmus and add a corresponding line that would act as the melody or have a soprano voice and add a corresponding line for the bass. All parts heard simultaneously should be independent from one another and the notes heard simultaneously should be in harmony. There can be different species of counterpoint and there can be more than two voices, usually up to four.