Sing "do–re–mi–fa–sol–la–ti…" and stop on ti. Feel it? You're hanging off a ledge, aching for that last step up to do. That one note — the 7th degree of the scale — is the engine behind almost every satisfying resolution in music. It even has a name for the job: the leading tone.
The 7th sits a half step below home
Walk the major scale and every gap is a whole step — except two half steps, and one of them is the very last one, from the 7th up to the 8th (which is home again). In C major:
That final H is the whole story. The 7th degree (B) is the only note sitting just a half step below the tonic (C). Every other note is a whole step or more away, with room to relax. B has nowhere to relax — it's one tiny step from home, leaning hard.
Half step below = maximum pull. Compare the 6th degree, A: it's a minor third (three half steps) below C — comfortable, no urgency. The 7th has only one half step left to travel, so its tension is maxed out. That single-step difference is what makes the 7th special, not the note itself.
That's why it's called the "leading tone"
The name is the behaviour: the leading tone leads your ear home. Its pull points upward, by a half step — B wants to rise to C. Leave it hanging and the music feels suspended, up in the air; let it resolve and you get that click of arrival.
It's what makes the dominant chord want to move
Here's where the leading tone stops being a curiosity and starts running the show. The most restless chord in a key is the dominant, V (→ why I, IV, V). In C major that's G major = G · B · D — and look who's living inside it:
That B is the leading tone. The dominant chord contains the note that aches to rise to the tonic, so the whole chord inherits that ache. When V moves to I, the B climbs a half step into C and the music lands home:
Strip the leading tone out and the dominant loses its nerve — which is exactly minor's problem.
Minor's missing leading tone → harmonic minor
Natural minor doesn't get a leading tone for free. Look at A minor (the relative of C major — same seven notes, different home):
The 7th, G, sits a whole step below home. No half step, no urgency — the pull home is weak. And it shows up in the chords: the dominant of A minor comes out as v = E minor (E · G · B), and E minor → A minor is a limp, unconvincing landing.
The fix is to raise the 7th by a half step — G becomes G♯ — manufacturing a leading tone where nature left none. This altered scale is harmonic minor, and now the step home is a half step again, just like in major:
Raising that one note revives two things at once:
| Natural minor | Harmonic minor (raised 7th) | |
|---|---|---|
| 7th → home | G → A, whole step (weak) | G♯ → A, half step (strong pull) |
| Dominant chord | Em (minor v) | E major (V!) — E · G♯ · B |
So "why does minor's V turn major?" has a one-word answer: the leading tone. Raising the 7th to G♯ changes the fifth chord's middle note from G to G♯, turning E minor into E major, and now E → Am resolves with real force.
That raised 7th is an accidental, not part of the key signature. A minor's key signature has no sharps, so the G♯ is added note-by-note wherever it's needed. If you keep seeing a sharp that "shouldn't" be in the key, it's often this borrowed leading tone at work.
In one line: the 7th scale degree sits a half step below the tonic, and that closeness gives it a powerful upward pull home — it's the leading tone that drives V → I cadences, and the note minor has to raise (harmonic minor) to make its dominant strong.