In simple counterpoint all parts must remain in the same relative position to one another.
The Cantus Firmus is a given melodic phrase that is to receive contrapuntal treatment, that is, one or more parts are to be added above or below it.
The Counterpoint is any part other than the Cantus Firmus.
Intervals are harmonic or melodic.
An Harmonic interval is the difference in pitch between two tones sounding at the same time.
A Melodic interval is the difference in pitch between two tones sounded in succession by the same voice. [[Fig. 1.]]
| Fig. 1. |
Harmonic intervals are divided into Consonances and Dissonances.
Consonances are classed as perfect or imperfect.
The Perfect consonances are the Unison, Fifth, and Octave. [[Fig. 2a].]