Which musical intervals are traditionally considered consonant in Western tonality?

In Western tonality, musical intervals are traditionally categorized based on their perceived stability, with consonances representing sounds of repose and dissonances representing tension.12

Consonant intervals are divided into two main groups:

• Perfect Consonances: These include the prime (unison), octave, and fifth. The perfect fourth is also considered a consonant interval, though it is treated as a dissonance when it occurs against the bass in contexts such as two-part counterpoint.3
• Imperfect Consonances: These include major and minor thirds and sixths. While these were historically considered dissonant or "imperfect" in early music theory, they became widely accepted as consonant by the 15th century, significantly enriching harmonic composition.314

Conversely, seconds, sevenths, and all augmented or diminished intervals are traditionally categorized as dissonances. These dissonant intervals are essential to Western harmony, as they create the tension that requires resolution to a stable, consonant harmony, thereby driving the musical flow.32