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Grade Six Music Theory - The Rules of Harmony

These rules of harmony need to be learnt. You need to use them when you are harmonizing a melody, creating a bass line with figured bass, or realizing a figured bass.

Click on each rule for more details about it.

 

The Rules

1a. NO consecutive 5ths
1b. NO consecutive octaves
1c. NO hidden (or “exposed”) consecutives

2a. NO dissonant leaps (seventh, augmented or diminished intervals), choose small intervals. Leading note resolves to the tonic.
2b. The soprano line should have an interesting melody.
2c. The alto and tenor lines should not move about much at all.

3a. Double the root or fifth in root position chords. Double any note in first inversion chords. Double the fifth in second inversion chords. Double the third in diminished chords. Double the third with care in other chords.
3b. Never leave out a figured note. Never leave out the root or third.

4a. Never overlap parts.
4b. Stay in the accepted voice ranges and don’t put more than an octave between the upper voices.

 

 1a. Consecutive 5ths
Consecutives are the no.1 bad guy in figured bass! You must NEVER write consecutives.
Consecutive 5ths often sneak in when there are two root position (5-3) chords next to each other.


Here are two root position chords – C major and A minor:
consecutive 5ths
In the first chord, the tenor and bass parts are a perfect 5th apart. In the second chord, they are also a perfect fifth apart.

When there are perfect 5ths in the same two parts one after the other, we call them “consecutive 5ths”.

We need to find another way to write one of the chords, to get rid of the consecutives:
fixed consecutive 5ths
Now the perfect 5th in the second chord is between the alto and tenor parts – the 5ths are no longer consecutive, because they are in different parts.

You have to check for consecutive 5ths between each voice of the harmony. This means six checks between each chord:


 Soprano – Alto
Soprano – Tenor
Soprano – Bass
Alto – Tenor
Alto- Bass
Tenor – Bass

 

Sometimes the consecutives are more difficult to see: here are consecutive 5ths between the alto and bass parts:
consecutives between alto and bass

Common questions about Consecutive 5ths:


Are compound 5ths (i.e. an octave and a 5th) wrong ? YES, they are also illegal.
Are diminished 5ths wrong? No, but you should still avoid writing them if possible.
Does it count if the same notes are repeated? No, consecutives are only bad when the voices move:
these are allowed
This is allowed, because the parts don’t change notes.

 

 1b. Consecutive Octaves
Consecutive octaves are just as bad as consecutive 5ths. Consecutive octaves can sneak in just about anywhere, so always be on the look out for them!

Check for consecutive octaves between all six voice pairings, as above.

Here are some illegal consecutive octaves:
consecutive octaves
Consecutive 5ths and octaves are considered to be bad because it sounds as though the music has been reduced to only three parts. Each of the four voice parts should have a strong, independent identity, and this effect is dramatically lessened by consecutives.

 

 1c. Hidden Consecutives
Also known as “concealed” or “exposed” consecutives, these are a little harder to spot, but must be avoided.
Hidden consecutives happen when:

  • The bass and soprano parts form a perfect 5th or octave AND
  • The 5th/8ve is approached by similar motion AND
  • The soprano part is approached by a leap (not by step).

 

the fifth is between the soprano and bass
The bass and soprano parts form a perfect 5th.


similar motion in the soprano and bass parts
The 5th is approached by similar motion (both parts move upwards in the same direction, instead of one part going up and other part down (“contrary motion”) or staying the same (“oblique motion”).

 

soprano part contains a leap

The soprano part contains a leap (the interval between the two notes is wider than a 2nd).

 

 

 

 

 

 

 

 

We can fix a hidden consecutive by just fixing one problem from above.

We can change around the notes, so that the 5th (or octave) disappears:

fix one

 

We can change the similar motion to oblique (or contrary) motion:
fix two

Or, we could make the soprano part move by step, instead of a leap.

  

 2a. Voice Leading Basics
“Voice leading” is about how each note connects to the next one, in one voice part.

In all voices:
Leaps of a seventh are NOT allowed.
In major keys, diminished/augmented melodic intervals are NOT recommended.
Augmented 2nds and 4ths are NOT allowed.
6ths should be avoided.
Leading notes in dominant chords ALWAYS resolve onto the tonic of a tonic chord. (Bach didn't always do this, though!)
In a cadential 6-4, the 4 resolves to 3 and the 6 resolves to 5.
Always choose a semitone step if one is available.

 

 2b. Voice Leading - Soprano
In the soprano part, you should try to write a reasonably tuneful melody, but you should avoid leaps of more than a perfect 5th. Follow these guidelines:

The best intervals to use are 2nds and 3rds.
4ths and 5ths are OK, but should only be used in an emergency.
Repeated notes can be used, but the more you use the more boring your melody will be, so only use them if you are stuck.

 

Here is the beginning of a soprano line written by J.S. Bach:
Bach soprano line
Which intervals has Bach used here, and how many times?

Unison (2)
Second (7)
Third (1)
Fourth (1)
Fifth (1)
Sixth (1)
Seventh (0)
Augmented/diminished (0)

As you can see, a good soprano line is made up mostly of intervals of a 2nd.

 

 2b. Voice Leading - Alto and Tenor
In the alto and tenor parts, you are padding out the chords:
Always choose the nearest note that you can, without breaking any other rules (e.g. of consecutives or illegal intervals etc.)

If possible, repeat the previous note.
Otherwise, choose the next nearest note.
Leaps of 4ths and 5ths are ok, but use them sparingly.

 

Here’s some more Bach, with a typical alto line. Let’s see which intervals are used here:
Bach alto line
Unison (7)
Second (4)
Third (2)
Fourth, fifth, sixth, seventh, dim/aug (0)

In the alto and tenor parts, the most common interval to use is the unison (the same note!)

Sometimes you don’t have much choice about which note to write next. Here are some cases:

Leading notes ALWAYS resolve onto the tonic when possible.
In a cadential 6-4, the 4 resolves to 3 and the 6 resolves to 5.
Always choose a semitone step if one is available.

 

2c. Voice Leading -Bass

The bass line should be reasonably melodic, without too much repetition of adjacent notes.

The bass usually moves either by step, or by leaps of perfect 4ths and 5ths, or by leaps of 3rds. Octave leaps may be used in moderation.

The bass should not leap by a 7th, an augmented or a diminished interval.

The final note in the bass line of a piece must always be the tonic.

 

 3a. Doubling

All four-note chords need to double one note from the triad. But which one?

 

Double the Root:

  • In any 5-3 chord
  • In any 6-3 chord EXCEPT diminished chords (ii° or vii°)
  • Never in 6-4 chords

 

 Double the Third:

  • In any 6-3 chord EXCEPT if it is the leading note (which means chord Vb)
  • Never in 6-4 chords
  • Never in a 5-3 chord UNLESS:
    • it is a minor third and it’s your only choice
    • it is a major third AND the piece is in a minor key, AND it’s part of a V-VI progression.

 

Double the Fifth:

  • In any 5-3 chord
  • In any 6-3 chord EXCEPT diminished chords (ii° and vii°)
  • Always in 6-4 chords

 

Use this table for reference while you’re practising. The greyed out chords are not used in tonal harmony at grade 6.

The chord notes in brackets are OK but try not to use them unless you absolutely have to!

 

Notes to Double in Major Keys

I

ii

iii

IV

V

vi

vii°

Ia

iia

iiia

IVa

Va

via

vii°a

1, 5

1, 5 (3)

1, 5 (3)

1, 5

1, 5

1, 5 (3)

-

Ib

iib

iiib

IVb

Vb

vib

vii°b

1, 3, 5

1, 3, 5

1, 3, 5

1, 3, 5

1, 5

1, 3, 5

3

Ic

iic

iiic

IVc

Vc

vic

vii°c

5

5

5

5

5

5

-

 

 

Notes to Double in Minor Keys

i

ii°

III+

iv

V

VI

vii°

ia

ii°a

III+a

iva

Va

VIa

vii°a

1, 5 (3)

-

-

1, 5 (3)

1, 5

1, 3, 5

-

ib

ii°b

III+b

ivb

Vb

VIb

vii°b

1, 5 (3)

3

-

1, 5 (3)

1, 5

1, 3, 5

3

ic

ii°c

III+c

ivc

Vc

VIc

vii°c

5

-

-

5

5

5

-

 

 

Are you thinking –“I’ll never remember all this?”
Don’t worry – it’s a normal reaction! Here’s a Rule of Thumb which is easy to remember:

Root position – 1 or 5
First Inversion – anything goes
Second inversion – 5
Watch out for:

  • diminished chords (ii° and vii°) – ONLY double the third
  • chord VI in minor keys CAN double the third
  • Vb – CAN’T double the third

 

  3b. Omission

Sometimes it’s ok to leave out the fifth of the triad.

Never leave out a note that is figured. So, if you see “5-3”, you must include the third and the fifth. But if the chord is blank, it means you can leave out the fifth.
If you see “6-3”, you must include the fifth (it’s the “3” of the 6-3), but if you see just “6”, then you can leave out the fifth.

You can never leave out the fifth of a 6-4 chord.

Never leave out the third or the root.

 

 4a. Overlap
Don’t let your voice parts overlap. The soprano line must always be higher than all the rest, the alto must always be higher than the tenor. Be careful not to write parts which cross over like these two:
examples of overlap
In the first example, the alto part C is lower than the tenor E.
In the second example, the tenor C is higher than the alto B in the next chord.

It’s ok to let the bass and tenor parts share a note from time to time.

 

 4b. Range
When you write for four voices (soprano, alto, tenor and bass), you should keep to the normal range that those voices can sing:
normal voice ranges for soprano, alto, tenor and bass

These ranges are not absolutely fixed, but stay within them to stay safe!

Never have an interval wider than an octave between the tenor and alto, or alto and soprano parts. It’s ok to have more than an octave between the tenor and bass parts.

 

 

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