The iv chord is a minor triad built on the fourth scale degree (the subdominant), diatonic in minor keys, that serves a predominant function by moving toward the dominant (V) or a cadential 6/4 chord in a harmonic progression.
The iv chord is the triad built on scale degree 4 of a minor key. Stack a third and a fifth above the subdominant and you get a minor triad, which is why we write it with a lowercase Roman numeral. In A minor, that's D-F-A. In a major key, the same scale degree gives you a major triad, written as capital IV. Same root, same function, different quality depending on the mode.
Functionally, iv is one of the two main predominant chords (the other is ii°/ii in minor). Its job is to set up the dominant. Think of tonal harmony as a three-step trip, tonic to predominant to dominant and back home. The iv chord lives in that middle step. A huge clue to why it works so well is voice leading. Scale degree 4 sits one step above scale degree 3 and a half step below 5 in most contexts, so the chord's tones pull naturally into the dominant triad or into a cadential 6/4 that decorates it.
The iv chord lives in Unit 5: Harmony and Voice Leading II, which is the whole unit on predominant function. It supports learning objective AP Music Theory 5.2.A (identifying harmonic function and progression in performed and notated music), and it's the launching pad for AP Music Theory 5.6.A and 5.6.B, since iv-to-cadential-6/4 is one of the most common ways composers approach a cadence. Per PIT-2.K.2, the cadential 6/4 embellishes the dominant, and a predominant like iv is what typically comes right before it. If you can't spot iv doing its predominant job, the whole T-PD-D-T progression model in Unit 5 falls apart. It also shows up in part-writing, where you'll harmonize bass lines in minor keys and need iv as a standard option before V.
Keep studying AP Music Theory Unit 5
Visual cheatsheet
view galleryCadential 6/4 (Unit 5)
The iv chord is the classic setup move for a cadential 6/4. The progression iv to I6/4 to V is everywhere in 18th-century style, and PIT-2.K.2 tells you the 6/4 must sit on a stronger beat than the V it decorates. The predominant iv is what gets you there.
Predominant Seventh Chords (Unit 5)
Add a seventh to iv and you get iv7, which works exactly the same way functionally. PIT-4.A.13 says predominant sevenths fulfill the same harmonic function as predominant triads, with one extra rule. The chordal seventh has to resolve down by step.
The vi (VI) Chord (Unit 5)
VI is the weaker cousin in the predominant family. Per PIT-2.J.1, vi (VI) can act as a tonic substitute or a weak predominant, and it often passes the baton to iv or ii before the dominant arrives. A common chain is VI to iv to V.
Subdominant (Units 1 and 5)
Subdominant is the name of scale degree 4 itself, which you learn back in Unit 1. The iv chord is what happens when you build a triad on that note in a minor key, so the Unit 1 vocabulary word becomes a Unit 5 functional chord.
Expect multiple-choice questions that test whether you know iv (and IV) as one of the two primary predominant chords, alongside ii. Practice questions ask things like which two chords are the primary predominants in tonal music and why the subdominant chord works so well in that role. You'll also use iv actively in the part-writing FRQs. When you harmonize a figured bass or a melody in a minor key, iv before V is a stock move, and graders check that you handle the voice leading cleanly. Avoid parallel fifths and octaves moving from iv to V, since the roots are a step apart and every voice moving in the same direction is the classic trap. In contextual listening, you should be able to hear iv as the tension-building chord right before the dominant at a cadence.
Same scale degree, different quality. Capital IV is the major triad on scale degree 4 in a major key (F-A-C in C major). Lowercase iv is the minor triad on scale degree 4 in a minor key (F-Ab-C in C minor). They share identical predominant function, so analyses treat them as the same harmonic move. The case of the Roman numeral is just telling you the chord quality, and on the AP exam writing the wrong case is a real error.
The iv chord is a minor triad built on scale degree 4 (the subdominant), and it's diatonic in minor keys, while major keys get the major IV instead.
Its job is predominant function, meaning it sits between tonic and dominant and pushes the progression toward V.
iv frequently leads into a cadential 6/4, which then embellishes the dominant at a cadence (the iv to I6/4 to V pattern).
Adding a seventh gives you iv7, which keeps the same predominant function but requires the chordal seventh to resolve down by step.
When part-writing iv to V, watch for parallel fifths and octaves, since the roots are a step apart and parallel motion is the most common error.
Lowercase versus uppercase matters in Roman numeral analysis, so write iv in minor and IV in major.
The iv chord is the minor triad built on the fourth scale degree of a minor key. In A minor it's D-F-A, and it functions as a predominant chord that leads toward the dominant (V).
Functionally yes, but the quality differs. Capital IV is a major triad (diatonic in major keys) and lowercase iv is a minor triad (diatonic in minor keys). Both serve the same predominant role, and on the AP exam the case of your Roman numeral has to match the chord quality.
Predominant. The iv chord and the ii (or ii°) chord are the two primary predominants in tonal music. They prepare the dominant rather than acting as one.
iv is a primary predominant with a strong pull toward V, while vi (VI) is either a tonic substitute or a weaker predominant per the CED. You'll often see VI move to iv before the dominant, so vi tends to come earlier in the progression.
Most often it goes to V or to a cadential 6/4 chord that decorates V at a cadence. When iv moves to V, every chord tone changes, so use contrary motion against the bass to dodge parallel fifths and octaves in part-writing.