The subdominant chord is the triad built on the fourth scale degree (IV in major, iv in minor) that functions as a predominant harmony, meaning its job is to lead the ear toward the dominant chord before the music resolves back to tonic.
The subdominant chord is built on scale degree 4. In a major key it's a major triad labeled IV, and in a minor key it's a minor triad labeled iv. In C major, that's F-A-C. The name doesn't mean "weaker dominant." It means the chord sits a fifth below tonic, mirroring how the dominant sits a fifth above.
Functionally, the subdominant belongs to the predominant family. Tonal phrases follow a tonic-predominant-dominant-tonic (T-PD-D-T) pattern, and the subdominant is one of the two main chords (along with ii) that fills that predominant slot. When you hear IV, your ear expects V next. The subdominant also appears in the plagal cadence (IV-I, the "Amen" cadence), one of the few places it moves straight back to tonic instead of feeding the dominant.
Subdominant function is central to Unit 5 (Harmony and Voice Leading II: Chord Progressions and Predominant Function), which is literally named after the job this chord does. You first build the IV triad in Unit 3 when you learn triads on every scale degree, and you start using functional progressions and cadences in Unit 4. Unit 5 then asks you to place IV correctly inside the phrase model. If you can't identify and part-write predominant chords, you'll lose points on harmonic dictation, Roman numeral analysis, figured bass realization, and the part-writing FRQs. The T-PD-D-T model is the skeleton of nearly every progression the exam throws at you, and the subdominant is the PD you'll see most often alongside ii.
Keep studying AP Music Theory Unit 5qLEl9yuuHxrmZor
Dominant chord (Units 4-5)
The subdominant exists to set up the dominant. IV-V is one of the most common moves in tonal music, but it requires careful voice leading because the roots are a second apart, which makes parallel fifths and octaves easy to write by accident.
Submediant chord (Unit 5)
The submediant (vi) often comes right before the subdominant in progressions like I-vi-IV-V. Think of vi as a launching pad into the predominant zone, while IV is the predominant itself.
Authentic Cadence (Unit 4)
A strong authentic cadence is usually prepared by a predominant chord, so the full cadential formula often looks like IV-V-I (or ii-V-I). The subdominant is the runway; the V-I is the landing.
Circle of fifths (Units 1, 5)
Subdominant means "a fifth below tonic," the mirror image of the dominant a fifth above. That symmetry is why F is the subdominant of C and why IV-V-I outlines such a satisfying tonal frame.
You'll work with the subdominant in almost every question format. Multiple-choice questions ask you to identify IV (or iv) by ear or by score, often testing whether you know it belongs to the predominant function group. In harmonic dictation FRQs, you notate the bass line and Roman numerals of a progression, and IV shows up constantly in the predominant slot before V. In the part-writing FRQs (realizing figured bass and writing from Roman numerals), you have to voice IV-V correctly, which usually means moving the upper voices in contrary motion against the rising bass to avoid parallel fifths and octaves. Knowing that IV predicts V is also your best error-checking tool. If your dictation answer has IV moving somewhere weird like iii, double-check it.
Both start with "sub," but they're different scale degrees with different jobs. The subdominant is built on scale degree 4 (IV in major) and functions as a predominant that pushes toward V. The submediant is built on scale degree 6 (vi in major) and typically acts as a tonic substitute or a bridge into the predominant area, as in I-vi-IV-V. Quick memory hook: subdominant is a fifth below the tonic, submediant is a third below the tonic (mirroring how the mediant is a third above).
The subdominant chord is built on scale degree 4, written IV in major keys and iv in minor keys.
It functions as a predominant, meaning its main job is to prepare and lead into the dominant chord in the tonic-predominant-dominant-tonic phrase model.
The name means "a fifth below tonic," the mirror of the dominant a fifth above, not a weaker version of the dominant.
In a plagal cadence (IV-I), the subdominant resolves directly to tonic, which is the famous "Amen" sound at the end of hymns.
When part-writing IV to V, move the upper voices in contrary motion to the bass to avoid parallel fifths and octaves, a classic point-loser on the part-writing FRQs.
The subdominant shares predominant function with the supertonic (ii), so both fill the same slot in a progression before V.
It's the triad built on the fourth scale degree, labeled IV in major keys (like F-A-C in C major) and iv in minor keys. It functions as a predominant harmony that leads toward the dominant chord.
Because it sits a perfect fifth below the tonic, just as the dominant sits a perfect fifth above it. The "sub" means below, not lesser.
No. The subdominant is scale degree 4 (IV) and functions as a predominant, while the submediant is scale degree 6 (vi) and usually acts as a tonic substitute. In C major, the subdominant triad is F major and the submediant triad is A minor.
Most of the time, yes, because IV-V is the standard predominant-to-dominant move. But IV can also resolve directly to I in a plagal cadence, and it can expand tonic in patterns like I-IV-I.
It depends on the key. In a major key, IV is a major triad. In a natural or harmonic minor key, iv is a minor triad, though raising scale degree 6 (as in melodic minor) can turn it into major IV.