The Minor Key, and Why Its Dominant Is Major
Everything in this module so far has been in a major key. Minor keys use the same three functions and the same four cadences — and they have one problem that major keys do not, which is worth understanding because the solution is a scale you have already met.
The seventh degree is too far away
Take A minor: A B C D E F G. It uses the same seven notes as C major, heard from A instead.
Now build the chord on the fifth degree. E, G, B — E minor.
And look at the seventh degree of the scale: G. It is a whole tone below the tonic A, not a semitone.
That is the problem. The last two lessons were built on the leading tone: the note a semitone under the tonic that pulls into it, and that gives the dominant its address. A natural minor key has no such note. Its seventh is a whole step away, and a whole step does not pull.
Play E minor then A minor and you can hear it. It moves, it is perfectly pleasant, and nothing resolves. It is a landing, not an arrival.
So the key borrows one
The fix is to raise that seventh degree by a semitone — G becomes G♯ — and the pull comes back.
Do that, and the chord on the fifth degree changes with it: E, G♯, B is E major. The dominant of a minor key is a major chord, and that is not a quirk. It is the whole reason the alteration is made.
Written as numerals: the diatonic fifth degree of a minor key is v, minor, and the one that actually cadences is V, major. The case is not decoration — it is the difference between a chord that ends the phrase and one that does not.
That scale has a name you already know
A scale with the seventh raised is the harmonic minor, and its name says what it is for: it is the minor scale adjusted so that the harmony works — specifically, so that the dominant can be a dominant.
It is not a different key or a different mood. It is the minor key with the one note changed that its cadences need, and composers use the natural seventh everywhere else in the same piece without anybody minding.
That raised seventh has a cost, which is the gap it opens. From F to G♯ is a step and a half, the biggest jump in any common scale, and it is what gives the harmonic minor its distinctive sound — the one people describe as Middle Eastern or Spanish. It is a side effect of fixing the cadence.
What stays the same
The three functions do not change. i is the tonic, iv is the subdominant, V is the dominant, and i–iv–V–i is the same sentence the major key tells.
The cadences do not change either. V–i is authentic, iv–i is plagal, ending on V is a half cadence. Everything from the last lessons transfers.
Two things are different, and only two: the tonic chord is minor, and the dominant has to be borrowed.
The other degrees are worth a glance
In A minor, the chords on the third and sixth degrees are C major and F major — written III and VI, uppercase, because they really are major. This is why a minor key can sound so much warmer than expected: two of its seven chords are major, and they are the two that lead most naturally back to the relative major.
Common mistakes to avoid
- Writing v where the phrase cadences. Minor v is a real chord and it does not end anything. If the phrase resolves, it is V.
- Treating the harmonic minor as a scale to improvise over. It is a harmonic adjustment. Melodies in minor keys use whichever seventh fits the moment.
- Assuming a minor key is the sad version of the major one. It shares every note with its relative major. What differs is which note is home.
Now play
The drill below is entirely in minor keys and asks which cadence you heard. The four are the same four.
Every dominant in them is the raised one — the major V — because the natural v does not cadence at all, which is the lesson stated as a rule the drill obeys. What varies is which of the four endings you are hearing, in a key whose tonic chord is minor.
If an authentic cadence in minor sounds darker than the ones you drilled in major, that is real and it is not the cadence: the chord it lands on is minor. The pull that got you there is identical.