In the context of [[tonal harmony]], perfect unisons, fifths, and octaves comprise one of two categories of consonant intervals known as *perfect consonances*—the other being [[imperfect consonances]]. Because of their simple mathematical ratios, perfect consonances have historically been regarded as more stable intervals than imperfect consonances and have accordingly been more strictly regulated in counterpoint, leading to the avoidance of certain [[forbidden motions]]. **Example 1.** Perfect consonances. ![[example perfect consonances.png]]