The chords ii7 and vii°7 are in a group of chords called secondary 7ths. A secondary 7th is an added 7th chord built on any degree of the scale except the dominant. (The dominant 7th is the only “primary 7th” chord).

Here are the secondary 7th chords in C major:

secondary 7ths C major

Here are the secondary 7ths built from the A harmonic minor scale (the melodic minor scale is sometimes used too.):

secondary 7ths A minor

We have already seen that vii°7 behaves in the same way as V7, the dominant 7th, and that ii7 often precedes a cadence.

The other secondary 7ths are less common. Quite often they move to the chord which is a 4th higher, for example chord iii7 can move to chord vi, or vi7 can move to chord ii. Another interesting fact which can help with understanding progressions, is that a secondary 7th is like a combination of two triads. Chord IV7 is a combination of chord IV and chord vi, for example. This means chord IV7 can be used in places where either a standard chord IV or a chord VI would also work, for example IV-V could be altered to IV7-V, or VI-iii could be altered to VI7-iii.

Here is an example of iv7 in Bach’s Chorale 100. The key is C minor at this point, so iv7 is F-Ab-C-Eb. The following chord is V.

chord iv7

Chorale 14 has an example of chord vi7 in G major (E-G-B-D). This time the secondary 7th moves by step to chord vii°.

chord vi7

7ths Voice Leading

Everything you have already learned about the voice leading of dominant and diminished 7th chords also applies to the secondary 7ths.

In older styles (Baroque and early Classical) the 7th is normally prepared in same part of the previous chord. In later styles it is not always prepared, but if the added 7th does occur in the previous chord, it is normally placed in the same part.

In all styles, the 7th will normally resolve downwards by step when the chord changes. Where this is not possible, it is usually held over and resolved in the next possible chord instead.

Here are some examples.

Typical behaviour, all styles. The 7th in vi7 (G) is prepared in the alto of chord Ib, then resolves down by step in the alto of chord ii.

typical 7th voice leading

Later styles only: The 7th in vi7 is not prepared, but it is approached smoothly by step and still resolves downwards by step.

unprepared 7th

All styles, less common: The 7th in vi7 cannot resolve in chord iii (because there is no F in this chord), so it is held/repeated and resolves at the next opportunity.

unresolved 7th