Progressions and harmonic movement

Three chords, and by the third one you feel you've arrived somewhere. Press play and let it loop.

That's a ii-V-I, the most common way into a home chord in jazz and a staple of pop and soul. Before you look at the piano roll: do you think the feeling of arrival comes from all four notes of the G7 moving, or from just one or two of them?

Two notes do most of the pulling

Look at the last change. G stays where it is. Two notes move, each by the smallest step there is:

• B rises to C. B is the leading note, one semitone under home, and in this kind of music it almost always resolves upwards.
• F falls to E. F is the seventh of G7, and it tends to resolve downwards.

B and F are six semitones apart, a tritone, the tensest interval in the chord. When both step inwards by a semitone, the tension collapses into the C major third, C and E. That's the click of a key turning in a lock, and you can hear it with just those two notes. Play B and F together on a keyboard, then C and E. Even without the rest of the chord, it sounds like an arrival.

So "G7 is tense and C is relaxed" is true but vague. The more useful explanation is that two voices each want to take one small step, and C major is where they both land. The pull in a progression lives in a few moving voices, not in the chord names.

Switch to root position and the same chords jump around as blocks. The arrival is still there (the bass moving from G to C helps a lot) but it's less smooth, because the B and F no longer walk to their neighbours.

Ways to end a phrase

A cadence is a musical punctuation mark: harmony and rhythm agreeing that a phrase has ended, or paused. A few you'll hear everywhere:

Cadence	Chords in C	How it lands
Perfect (authentic)	G (or G7) to C	A full stop
Plagal	F to C	Softer, the "Amen" at the end of many hymns
Half	Anything to G	A comma: a question left open
Deceptive	G to Am	You expect home and get somewhere else

Timing matters as much as the chords. Hold the G7 short and the C long, and the C sounds final. Flip the lengths, or stop on the G7, and the same chords feel unfinished.

Change where it lands

Here's the same ii-V-I, but now you can move the last chord.

Move it down 4 and the G7 lands on A♭ major instead of C: a big, cinematic swerve you'll recognise from countless film cues and power ballads. Down 3 gives A major, bright and slightly startling. Up 5 gives F major, softer, as if the phrase took a step sideways. Each one only works as a surprise because the G7 had already promised C. Expectation is the material; the landing is what you do with it.

Borrow a chord from next door

Now a famous trick: take a major chord from the home key and make it minor, just for a moment.

Between F and F minor, only one note moves: A sinks to A♭. Then A♭ sinks one step further to G as C comes home. That falling line, A, A♭, G, is a little sigh, and to many listeners it sounds bittersweet, like a happy memory with a shadow across it.

This is a borrowed chord: F minor belongs to C minor, not C major, but you can borrow it without leaving C. Musicians often call it the "minor four" (written iv, where the usual chord is IV). You can hear it in Radiohead's "Creep", where a major chord turns minor on the way back round, and in the Beatles' "In My Life". Borrowing doesn't move the home. Everything around it still points to C.

Numbers instead of names

Musicians often write progressions as Roman numerals counted from the home note, so the pattern survives in any key. In C major: I is C, ii is Dm, IV is F, V is G, vi is Am. Uppercase means major, lowercase minor.

That's how you can say "I-V-vi-IV" and every guitarist knows you mean the four chords behind a huge number of pop songs, whether they play them as C, G, Am, F or as D, A, Bm, G. It's the same idea as a melody's step pattern in Pitch and intervals: the relationships matter, not the starting note.

A detour that points somewhere new

A secondary dominant borrows the pull of a V chord and aims it at a different target. In C major, D7 (D, F♯, A, C) points at G the way G7 points at C, because F♯ is a leading note to G. Try C, Am, D7, G, C instead of C, Am, F, G, C. The trip to G suddenly has a signpost.

One outside chord doesn't change the key. A modulation is when the home really moves: a new leading note, new cadences and new arrivals, held long enough that the old home stops feeling like home. The classic pop version is the last-chorus key change, everything lifted a step or so to raise the stakes. Software that names a song's key faces the same question from outside: Chord and key recognition shows why a key estimate is a summary over time, and how a borrowed chord or a modulation can tip it.

Not all music moves this way

Cadences and leading notes belong to a particular tradition, centered on European and American harmony. Plenty of music generates its motion differently. A rock riff over a single chord can drive for minutes. A lot of West African and Afro-Cuban music builds momentum from interlocking cycles that never resolve. In Hindustani music, the drone holds the home steady while the melody does all the travelling. And a pop loop like Am, F, C, G can go round for a whole song without ever deciding to land, which is part of its hypnotic pull.

So "G7 wants to go to C" is shorthand for "listeners raised on this kind of music expect it to". It's a strong, learnable expectation, not a law of sound.

Same idea, different place: a model like Maru's Chord Seq learns which chord tends to come next by studying lots of progressions, much as you learned to expect C after G7. Its suggestion is an estimate shaped by what it heard, and like you, it can be surprised. See What an audio model learns.

Make it yours

Start with C, Am, F, G. Make two new versions, keeping the rhythm and melody the same:

1. Swap F for Fm (the borrowed minor four).
2. Swap F for D7 (the secondary dominant pointing at G).

For each, find the one note that changed and where it goes next. Then decide which version you'd use for which kind of song. Write the progression down as numerals too (I, vi, iv, V); it'll work in any key you sing in.

Quick check

1. G7 goes to C. Which two notes do most of the work, and how far do they move? B rises to C and F falls to E, each by one semitone. The tritone between them closes into a third. It's tempting to credit the bass, and the bass helps, but those two inner moves carry the arrival even on their own.
2. A song in C major plays F minor in the chorus. Has it changed key? Probably not. A single borrowed chord colours the home key; for a real key change you'd need new cadences and arrivals that keep pointing somewhere else.
3. You expect G7 to resolve to C, and it goes to A♭ instead. Is that a mistake? No, it's a deceptive move, and it only works because the expectation of C was there. Surprise is a tool. Whether it's the right one depends on the moment in the song.

Next steps

• Go deeper: Melody and motifs. The chords move now, but people hum the melody on top. What makes a few notes stick?
• Use it: Harmony in performance. Put borrowed chords and secondary dominants under your hands.