In AP Music Theory, consonance is the stable, restful quality of certain intervals and chords (unisons, octaves, perfect fifths, and major/minor thirds and sixths), in contrast to dissonance, which creates tension that wants to resolve.
Consonance is the sound of stability. When two notes form a consonant interval, your ear hears them as agreeing with each other. Nothing feels unresolved, nothing is pulling anywhere. The standard consonant intervals are the perfect unison, perfect octave, perfect fifth, and the major and minor thirds and sixths. Everything else (seconds, sevenths, and the tritone) is dissonant, meaning it creates tension that wants to resolve to something consonant.
On the AP exam, consonance shows up most directly in Topic 2.6, where you work with interval inversion. Here's the useful pattern. When you invert an interval (move the bottom note up an octave), consonance is almost always preserved. A minor third inverts to a major sixth, and both are consonant. A minor second inverts to a major seventh, and both are dissonant. The one tricky spot is the perfect fourth, which is the inversion of the perfect fifth. Even though it's a 'perfect' interval, the fourth is treated as dissonant in some voice-leading contexts. Knowing which intervals are consonant lets you predict how an inversion will sound before you even spell it.
Consonance lives in Unit 2 (Music Fundamentals II) under Topic 2.6, Interval Inversion and Compound Intervals, supporting learning objective 2.6.A, which asks you to identify interval inversions and compound intervals in both performed and notated music. The essential knowledge (PIT-1.M.1) gives you the inversion rules. An interval plus its inversion equals a perfect octave, perfect stays perfect, major flips to minor, and diminished flips to augmented. Consonance is the 'so what' behind those rules. The mechanical flipping matters because it tells you whether the resulting interval is stable or tense, and that stability judgment is what you'll lean on later when you analyze harmony, voice leading, and chord function. If you can hear and label consonance now, every later unit gets easier.
Keep studying AP Music Theory Unit 2
Visual cheatsheet
view galleryDissonance (Unit 2)
Consonance only means something because dissonance exists. Dissonant intervals like the minor second and major seventh create tension, and consonant intervals provide the resolution. Music is basically the back-and-forth between the two, and the AP exam expects you to sort intervals into these categories by ear and by eye.
Interval Inversion (Unit 2)
Inversion is where consonance gets tested in Topic 2.6. The sizes of an interval and its inversion add up to nine (a third inverts to a sixth), and consonant intervals almost always invert to other consonant intervals. That pattern lets you check your inversion work instantly. If a consonant interval inverted into something dissonant, you probably made a spelling error.
Perfect Fourth (Unit 2)
The perfect fourth is the famous exception. It's the inversion of the super-stable perfect fifth, yet it's treated as dissonant in certain contexts, especially when it occurs above the bass. This is the one place where inversion changes the consonance verdict, which makes it a favorite trap on multiple-choice questions.
Triad (Unit 3-4)
Major and minor triads are built entirely from consonant intervals (thirds, a fifth, and their inversions), which is why they sound stable and serve as the resting points of tonal harmony. Diminished and augmented triads contain dissonant intervals, which is why they feel unstable and need to resolve. Consonance is the reason chord quality has the sound it does.
You won't get a question that just says 'define consonance.' Instead, the concept hides inside interval questions. A typical multiple-choice stem gives you an interval, often labeled consonant or dissonant, and asks for its inversion. For example: a dissonant harmonic interval of a minor second is inverted, so what results? Apply the rules (sizes sum to nine, minor becomes major) and you get a major seventh, which is also dissonant. Aural questions can play this same game, asking you to identify whether a performed interval sounds stable or tense before naming it. Per learning objective 2.6.A, you need to handle this in both performed and notated music, so practice hearing the difference, not just spelling it.
Consonance and dissonance are opposite ends of the same spectrum, not unrelated ideas. Consonant intervals (unison, octave, fifth, thirds, sixths) sound stable and at rest. Dissonant intervals (seconds, sevenths, the tritone, and contextually the perfect fourth) sound tense and unresolved. The quick test is to ask whether the interval could comfortably end a piece. If yes, it's consonant. If it makes you wait for the next note, it's dissonant.
Consonant intervals are the perfect unison, perfect octave, perfect fifth, and the major and minor thirds and sixths; they sound stable and restful.
Dissonant intervals (seconds, sevenths, and the tritone) create tension that pulls toward a consonant resolution.
When you invert an interval, consonance is preserved in almost every case, so a minor second (dissonant) inverts to a major seventh (also dissonant).
The perfect fourth is the exception: it's the inversion of the consonant perfect fifth but is treated as dissonant in some contexts.
Inversion rules from PIT-1.M.1 make consonance predictable: sizes sum to nine, perfect stays perfect, major flips to minor, and diminished flips to augmented.
Knowing consonance now pays off later, since stable triads are built from consonant intervals and harmonic motion is driven by dissonance resolving to consonance.
Consonance is the stable, restful quality of certain intervals and chords. The consonant intervals are the perfect unison, perfect octave, perfect fifth, and the major and minor thirds and sixths. They sound resolved, unlike dissonant intervals, which create tension.
It depends on context, which is exactly why the exam loves it. The perfect fourth is the inversion of the consonant perfect fifth, but in some voice-leading situations (especially above the bass) it's treated as dissonant. Treat it as the one exception to 'consonance survives inversion.'
Almost never. A minor third inverts to a major sixth (both consonant), and a minor second inverts to a major seventh (both dissonant). The perfect fourth/fifth pair is the only case where the consonance verdict can shift.
Consonant intervals sound stable and could comfortably end a piece, while dissonant intervals sound tense and need to resolve. Unisons, octaves, fifths, thirds, and sixths are consonant; seconds, sevenths, and the tritone are dissonant.
A major seventh. Interval sizes sum to nine (2 + 7 = 9) and minor becomes major when inverted, and since the minor second is dissonant, its inversion is dissonant too. This is a classic Topic 2.6 multiple-choice question.