What does 6/4 mean in figured bass?

It asks for the notes a sixth and a fourth above the bass, which makes a triad with its fifth in the bass. Over C that is A and F, so the chord is F–A–C.

The first inversion of a seventh chord. Over B in the bass, 6/5 asks for G and F, and the understood third, D, completes B–D–F–G, which is G7.

What does a sharp under a bass note mean?

A lone sharp stands for the third above the bass, raised. Under E in A minor it asks for G♯, which makes the chord the major V.

Why do some bass notes have no number?

No number is the default: a root-position triad with its third and fifth understood. The player adds them unless a figure says otherwise.

Figured Bass: What the Numbers Under the Bass Mean

Figured bass writes a chord as numbers under its lowest note, each an interval above it. Nothing means a root-position triad, 6 a first inversion, 6/4 a second; 7, 6/5, 4/3 and 4/2 are the seventh chord’s positions.

What do the numbers under a bass note mean?

Each number is an interval measured up from the bass note, counted the way any interval is: both ends included, accidentals ignored. A 6 under a bass note asks for the note a sixth above it, a 4 the note a fourth above, and so on. The player fills in the rest of the chord from the key. The system comes from Baroque keyboard playing, where a player read a bass line with figures and improvised the chords above it.

Because most chords are triads, the numbers every triad has are left out. A root-position triad would be 5/3, and nobody writes it: no figure at all means 5/3. The same shorthand trims the other chords, so a first inversion that would be 6/3 is written just 6.

One C major triad over three different basses: nothing under C, 6 under E and 6/4 under G.

G7 over its four basses: 7 under G, 6/5 under B, 4/3 under D and 4/2 under F.

Written	Complete	Position	Numeral
—	5/3	Root position	I
6	6/3	First inversion	I⁶
6/4	6/4	Second inversion	I⁶₄
7	7/5/3	Seventh chord, root position	V⁷
6/5	6/5/3	Seventh chord, first inversion	V⁶₅
4/3	6/4/3	Seventh chord, second inversion	V⁴₃
4/2	6/4/2	Seventh chord, third inversion	V⁴₂

What do accidentals in the figures mean?

A sharp, flat or natural beside a number alters that interval above the bass: ♯6 asks for a raised sixth. An accidental on its own stands for the third, so a lone ♯ under a bass note asks for a major third above it, which is how a major chord is written in a minor key. A natural cancels a sharp or flat the key signature would otherwise give. A 6 with a stroke through it means the same as a sharp beside it: raise the sixth.

In A minor: a lone ♯ under E for G♯, the raised third of V; a plain 6 under G♯ for V⁶; and a slashed 6 under B for vii°⁶, whose G♯ is a raised sixth above the bass.

What is the cadential 6/4?

A 6/4 above a bass on the dominant note looks like a second inversion of the tonic, but it does not behave like one. In the cadential 6/4 the bass holds the dominant while the upper notes fall by step onto the fifth and the third of the dominant chord, so the chord is really a decoration of V, arriving on the strong beat just before it. The figures say so: 6/4 followed by 5/3. A 6/4 whose bass moves by step between two chords, as V⁶₄ in I–V⁶₄–I⁶, is a passing 6/4.

The cadential 6/4 in C: G holds in the bass, C falls to B and E falls to D, and the music lands on I.

How do you play from a figured bass?

Read the bass note and the key. Notes the key signature alters stay altered, unless a figure says otherwise.
Read each figure as intervals above that bass note: the 6 in 6/4 is the note a sixth above, the 4 the note a fourth above.
Add the understood notes: a third and a fifth over a bare bass, a third under a 6 (it is 6/3), nothing more under a 6/4, a third and a fifth under a 7. Then apply any accidentals to the notes they sit beside.

Figured bass