Which interval is considered consonant among the options?

• A. Unison
• B. Major Second
• C. Perfect Fifth
• D. Tritone

Answer: (C)

Consonance in intervals comes from how cleanly the overtones of two notes align. The perfect fifth has a simple 3:2 frequency relationship, so its overtones align very smoothly. That strong, stable blend is why it’s such a foundational and highly consonant interval in Western harmony.

A major second, while not extremely dissonant, has a more complex overtone interaction that creates beating, which listeners perceive as less stable than the perfect fifth. A tritone splits the octave in a way that produces a pronounced sense of tension, historically treated as dissonant and needing resolution. Unison involves the same pitch, so there’s no real interval between different pitches, and while it is consonant, it doesn’t function as an interval of harmony between distinct notes.

So, among the options, the perfect fifth stands out as the classic, strong consonant interval.