Modes Explained

Modes Explained 6: Chord/Scales

This post looks at applying modes in the context of melodic construction (such as in composition or improvisation) over a predefined chord progression. Specifically we are going to learn about scale choices, and finding the most appropriate modes and scales for given chords. In fact, modes and chords are really just two different ways of thinking about what is essentially the same thing (so its definitely worth making sure that your chord theory is up to scratch).


Generally, western music consists mostly of three basic chord qualities – major, minor and dominant seventh. The major chord formula is 1, 3, 5 while the minor chord requires a minor third so its formula is 1, b3, 5. Dominant seventh chords are a major triad with a b7 added on top, so the dominant 7th formula is 1, 3, 5, b7.

Of course, the major and minor chords can also be played as seventh chords, with a major seventh chord having the formula 1, 3, 5, 7 and the minor seventh being 1, b3, 5, b7.

Major 7th 1, 3, 5, 6, 7
Minor 7th 1, b3, 5, 6, b7
Dominant 7th 1, 3, 5, 6, b7

All of these chords can be extended beyond the seventh with natural tensions up to a thirteenth – basically this means just stacking thirds above the seventh, without using flattened or sharpened degrees. The natural tensions above a seventh chord are therefore the 9th, 11th and 13th. We can add these notes to our major 7th, minor 7th and dominant 7th chords to create the major 13th, minor 13th and dominant 13th chords respectively.

Major 13th 1, 3, 5, 6, 7, 9, 11, 13
Minor 13th 1, b3, 5, 6, b7, 9, 11, 13
Dominant 13th 1, 3, 5, 6, b7, 9, 11, 13

Scale Choices

When choosing which modes to use over a given chord progression its important to always be aware that every mode implies a harmony, and that every mode co-exists with some sort of chord. One way of determining what chord relates with which mode, is to take the notes of the chord and rearrange them so that they fit into one octave – this means bringing the 9th down an octave to the 2nd, the 11th down to a 4th and the 13th down to a 6th.

Major 13th 1, 2, 3, 4, 5, 6, 7
Minor 13th 1, 2, b3, 4, 5, 6, b7
Dominant 13th 1, 2, 3, 4, 5, 6, b7

Of course, we’ve already encountered these exact same formulas – but with different names. For instance the Maj13 formula is the same as the ordinary major scale/Ionian mode; the min13 formula is the Dorian mode, while the dominant 13th formula is the same as the Mixolydian mode.

This means that a Maj13th chord implies the Ionian mode. Similarly, a person soloing in a Dorian mode is implying min13th harmony. In fact, these modes and their respective harmony are so intertwined that its helpful to think of a maj13th chord as being meaning Ionian – and vice versa. Rather than thinking about chords and scales distinct from each other, its good to start thinking about ‘chord scales’ where terms like Ionian and major, or Mixolydian and dominant are two words for exactly the same concept.

Major 13th/Ionian Mode 1, 2, 3, 4, 5, 6, 7
Minor 13th/Dorian Mode 1, 2, b3, 4, 5, 6, b7
Dominant 13th/Mixolydian 1, 2, 3, 4, 5, 6, b7

‘Avoid’ Notes

An avoid note is a note of a mode, that creates an ‘unacceptable’ dissonance when held against the chord of the mode. For example, the Ionian mode is a suitable scale choice for a maj13 chord – but if you hold the 4th against a maj13 chord, the note will ‘need’ resolution if it is to sound ‘acceptable’. The sound of the 4th degree against a maj13 chord is almost universally agreed upon as sounding ‘wrong’ (or at least, not quite ‘right’).

Notes such as these are known as ‘avoid’ notes and need to be treated carefully when being used in melodic construction. Although they are called avoid notes, there is no need to avoid them completely – just use caution.

The Cause of Avoid Notes

Avoid notes are a result of the interval of a minor 9th (e.g. E to F, B to C etc). From the previous example, the reason the F sounds so unpleasant is because it clashes with the note E in the chord (a Cmaj7 contains the notes C E G B). Other instances of avoid notes include the 4th degree of a Mixolydian mode – e.g. a C over a G7 chord. G7 has the notes G B D F, but playing a C in the melody will clash with the B in the chord.

Dealing with Avoid Notes

Not all occurrences of a minor 9th will necessarily sound unmusical. Depending on the player, the voicing of the chord, and the expectations of the listener, its perfectly possible for an F to be played over a Cmaj7th chord (or a C over a G7 for that matter). Nonetheless, the minor 9th interval will typically sound unpleasant, so its important to be familiar with the common methods of dealing with these ‘clashes’.

The strident sound of avoid notes can be lessened by using the note as a ‘passing’ note. For our purposes, a passing note is a note which is usually of short duration and resolves stepwise to the note immediately below or above it. For example, in the case of an F over a Cmaj7 chord, keeping the F short and resolving it immediately to the E below, or the G above it would prevent the F from sounding ‘wrong’.

The other accepted way to deal with avoid notes is to raise them by a semitone – thus turning the ugly minor 9th interval into the much nicer sounding major 9th interval. In the case of the Cmaj7 chord this would mean raising the F to F#. This way the E in the chord will no longer clash with the melody note.

When raising notes to avoid the minor 9th dissonance it is important to be aware of the way that it will effect the ‘character’ of the melody. In ‘Top 40’ rock and pop songs or any music with a mostly static key centre, the raised note will sound like its ‘out of key’ – because, after all, that is exactly what it is. On the other hand, in many jazz tunes, some virtuoso rock guitar pieces, or any piece with ambiguous or changing key centres, or in a ‘modal key’, then the raised note may not sound so contrived or out of place.

Lydian Chords

As we know from the previous modes post the Lydian scale formula is 1 2 3 #4 5 6 7. Rearranging these notes into stacked thirds to create a chord and moving the 2, #4, and 6 up an octave we arrive at the chord formula 1 3 5 7 9 #11 13, which is the formula for a maj13#11 chord.

Of course its not necessary to use all of the possible notes to build chords. For instance using only degrees 1, 3 and 5 we can construct an ordinary major triad, or if we take degrees 1, 2 and 5 we can build a sus2 chord. More complex chords that can be derived from the Lydian mode includes the maj69 chord (1, 3, 5, 6, 9) or the maj7#11 chord (1, 3, 5, 7, 9, #11).

The most common chords that can be derived from the Lydian mode include maj, sus2, maj6, maj7, maj9, maj7#11, maj13, add9 and maj69 chords. As such Lydian can be a good choice for soloing over all of these chords.

Ionian Chords

The Ionian formula is 1 2 3 4 5 6 7. Rearranging these notes into stacked thirds to create a chord, we arrive at the chord formula for a maj13 chord, 1 3 5 7 9 11 13. Other chords which can be constructed from the notes in the Ionian mode are maj, sus2, sus4, maj7, maj9, maj11, maj13, add9, and maj69 chords.

You may notice that many of those chords can also be derived from the Lydian mode which means you have a choice of Ionian or Lydian as the mode to base your melodies on. Bear in mind though that the 4th degree of the Ionian mode will clash with the 3rd of the chord – i.e. the 4th note of the Ionian mode will be an avoid note. So be cautious, perhaps treating it solely as a passing note. Of course, you also have the option of raising the avoid note – but then you would just end up playing the Lydian mode anyway, since Lydian is essentially a major scale with a #4.

Mixolydian Chords

The Mixolydian formula is 1 2 3 4 5 6 b7. There are various chords which can be created from these notes such as the simple maj, sus2 and sus4 triads, and triads with added notes such as the add9 and maj69 chords. However, be aware of the natural 4th which will be an avoid note on the maj, add9 and maj69 chords. Of course, the sus chords do not have a third so there is no problem with an avoid note on those chords.

Mixolydian is ideal for dominant 11th chords (though to be honest these don’t come up often), and is also suitable over 7th, 9th and 13th chords – but again be aware of the avoid note. Mixolydian is perfectly suited to suspended dominant chords such as 7sus4, 9sus4 and 13sus4, because there is no avoid note.

Dorian Chords

The Dorian formula, when rearranged as a chord is 1 b3 5 b7 9 11 13, which is the chord formula for a min13th chord. The Dorian mode is therefore the perfect choice over most minor chords, min7, min9, min11 and min13 chords. Also, because the Dorian mode has a natural 6th (13th) it is perfect for min6 and min69 chords.

As the Dorian mode does not contain the major third, there is no danger of the natural 4th being an avoid note. This is also true for the Aeolian, Phrygian and Locrian modes since none of these modes have a major third.

Aeolian Chords

The Aeolian formula is 1 2 b3 4 5 b6 b7, which, when rearranged as a chord formula gives us a min7b13 chord formula, 1 b3 5 b7 9 11 b13. The only difference between the Dorian mode and the Aeolian mode is the presence of the b6 in the Aeolian. This makes Aeolian effective over min7, min9 and min11 chords, but will not work over min6, min69 or min13 chords as these chords all require the natural 6th/13th.

Also, even when used over basic min7, min9 and min11 chords we still have the issue of the b6 clashing with the 5 of the chord – i.e. the b6 is an avoid note. Because of this, it may be wise to stick to the Dorian mode over most minor chords. This is not to say that you can’t use Aeolian over min7 type chords – in fact, done carefully, I find that the b6 can be a beautifully ‘brooding’ note, providing that it is not held against the chord, and is used sparingly/tastefully.

Two chords which beg for the Aeolian mode to be used is the min7b13 and minb6 chords. Both of these chords a minor type chords, and both contain the b6/b13 note, so the Aeolian mode is the idea choice for these chords.

Phrygian Chords

The b3 and b7 indicate that the Phrygian mode is some kind of minor mode, however the presence of the b6 and a b9 (both avoid notes on min chords) makes it a less common choice over min7, min9, min11 and min13 chords. That said, used as passing notes the b6 and b9 make for a very dark, and, in my opinion, appealing sound, with a Spanish/Moorish flavour.

One chord that is particularly well suited to the Phrygian mode is the 7susb9. This chord is actually a dominant type chord – not a minor type chord – and it involves some fairly complicated theory to fully explain how and why this works. Unfortunately its well beyond the scope of this post, however later in the modes series we will look at it closer.

Locrian Chords

The Locrian formula is 1 b2 b3 4 b5 b6 b7, the notes of which build a min7b5 chord or simply Ø (meaning half-diminished). Since the half-diminished chord has a b5 (rather than a natural 5) there is no danger of the b6 being an avoid note as it was in the Aeolian and Phrygian modes. The only avoid note in the Locrian mode is the b9 which clashes with the root note. As with all other avoid notes mentioned in this post, this note is usually ‘brushed over’ as a passing note, or raised up to a natural 2nd.

In Summary

Today we’ve covered a LOT of material, so hopefully this table might make the most important things a little easier to digest.

Chord Name Applicable Mode(s) Mode Formula Avoid Notes
Major Triad Lydian 1 2 3 #4 5 6 7
Ionian 1 2 3 4 5 6 7 4
Mixolydian 1 2 3 4 5 6 b7 4
Sus2 Triad Lydian 1 2 3 #4 5 6 7
Ionian 1 2 3 4 5 6 7
Mixolydian 1 2 3 4 5 6 b7
Sus4 Triad Ionian 1 2 3 4 5 6 7
Mixolydian 1 2 3 4 5 6 b7
Minor Triad Dorian 1 2 b3 4 5 6 b7
Aeolian 1 2 b3 4 5 b6 b7 b6
Phrygian 1 b2 b3 4 5 b6 b7 b6, b2
Maj7 Lydian 1 2 3 #4 5 6 7
Ionian 1 2 3 4 5 6 7 4
Min7 Dorian 1 2 b3 4 5 b6 7
Aeolian 1 2 b3 4 5 b6 7 b6
Phrygian 1 b2 b3 4 5 b6 7 b6, b2
7 Mixolydian 1 2 b3 4 5 b6 7
(aka Min7b5)
Locrian 1 b2 b3 4 b5 b6 b7 b2

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