Chord Tensions (Extensions & Alterations)

7th Chords

In Jazz, rather than using triads as our basic chord, we add another note on top (either a minor 7th or a Major 7th) to create 7th Chords. This makes the chord sound a little more harmonically complex. The four basic types of triad can each be extended to create eight types of 7th chords.

Triad Derivation	7th Chord	Degree & Notes from C	Intervals	Notation	Sheet Music
Major	Major 7 Chord	1 3 5 7	1 to 3 = Maj 3rd 3 to 5 = Min 3rd 5 to 7 = Maj 3rd	CΔ7 CMaj7
		C E G B
	Dominant 7 Chord	1 3 5 ♭7	1 to 3 = Maj 3rd 3 to 5 = Min 3rd 5 to 7 = Min 3rd	C7
		C E G B♭
Minor	Minor 7 Chord	1 ♭3 5 ♭7	1 to 3 = Min 3rd 3 to 5 = Maj 3rd 5 to 7 = Min 3rd	Cm7 C-7
		C E♭ G B♭
	Minor Major 7 Chord	1 ♭3 5 7	1 to 3 = Min 3rd 3 to 5 = Maj 3rd 5 to 7 = Maj 3rd	CmMaj7 C-Δ7
		C E♭ G B
Diminished	Diminished 7 Chord	1 ♭3 ♭5 ♭♭7	1 to 3 = Min 3rd 3 to 5 = Min 3rd 5 to 7 = Min 3rd	Cdim7 Co
		C E♭ G♭ B♭♭
	Half Diminished 7 Chord	1 ♭3 ♭5 ♭7	1 to 3 = Min 3rd 3 to 5 = Min 3rd 5 to 7 = Maj 3rd	Cm7b5 Cø
		C E♭ G♭ B♭
Augmented	Augmented 7 Chord	1 3 #5 ♭7	1 to 3 = Maj 3rd 3 to 5 = Maj 3rd 5 to 7 = Dim 3rd	Caug7 C7#5 C+7
		C E G# B♭
	Augmented Major 7 chord	1 3 #5 7	1 to 3 = Maj 3rd 3 to 5 = Maj 3rd 5 to 7 = Min 3rd	CMaj+7 CMaj7#5 CΔ+7
		C E G# B

(Notice the Augmented 7th chord uses an interval of a Diminished 3rd. This is just a flattened minor 3rd (AKA a Major 2nd). This is done because if you were to add a Major 3rd on top of the #5 you would reach the root again.)

While there are eight types of 7th chords, the most important and most widely used are the:

• Maj7 chord;
• Dominant 7 (V7) chord; and
• m7 chord.

All the other types of 7th chords are generally used as substitutes for these three main chord types (e.g. a m7 chord can be substituted by a mMaj7 or half-dim chord; a V7 chord can be substituted by an Aug7 chord or a half-dim chord; etc.)

Chord Tensions (Extensions & Alterations)

The root, 3rd, 5th, or 7th of a chord (called Chord Tones) determine the type of chord that it is and so cannot be altered:

• The root establishes the chord tonality (CMaj7 vs DMaj7);
• The 3rd & 7th (called Guide Tones) establish the chord quality (CMaj7 vs C7 vs Cm7); and
• The 5th establishes whether the chord is diminished or augmented (Co vs Cø vs C+7).

We can, however, extend our basic 7th chord by adding yet more notes on top of the 7th, again building up in thirds. This gives us a 9th, 11th and 13th – these are called Chord Tensions. The degrees are still in reference to the Major Scale. Below is the C Major Scale with all the degrees over two octaves listed.

So:

• The D is both the 2 and the 9.
• The F is both the 4 and the 11.
• The A is both the 6 and the 13.
• The D♭ is both the ♭2 and the ♭9
• The F# is both the #4 and the #11.
• The A♭ is both the ♭6 and the ♭13.

In this way, we can build a chord with up to 7 notes that contains every note of the C Major Scale. Adding another note one 3rd above the 13th will get you back to the root (A plus a minor 3rd = C).

When reading notation, you in theory should play all the notes up to and including the highest tension listed, for example:

• CMaj7 = C E G B
• CMaj9 = C E G B D
• CMaj11 = C E G B D F
• CMaj13 = C E G B D F A

I say ‘in theory’ because in practice this is not actually the case. In practice, it is possible to omit notes that are not important or that are ‘unavailable tensions’. But we will cover this in future lessons.

These natural chord tensions can also be flattened or sharpened by 1 semitone to create altered chord tensions. In this way all 12 notes can be assigned a degree in relation to the root note of the chord. Generally, you would NOT add more than one of each tension degree to a single chord (i.e. if you have a ♮9, you would usually NOT also have a ♭9 or #9).

Below is list of all 12 notes with each allocated a degree based on chord type.

Note	C	C#/D♭	D	D#/E♭	E	F	F#/G♭	G	G#/A♭	A	A#/B♭	B
CMaj7	1	♭9	9	#9	3	11	#11	5	♭13	13	#13	7
C7	1	♭9	9	#9	3	11	#11	5	♭13	13	♭7	7
Cm7	1	♭9	9	♭3	♭11	11	#11	5	♭13	13	♭7	7
CmMaj7	1	♭9	9	♭3	♭11	11	#11	5	♭13	13	#13	7

So for example, a CMaj7 could be extended in the following way:

And again, we play all the notes up to and including the highest tension listed taking any alterations into account:

• CMaj9#11 = C E G B D F#
• CMaj13#11 = C E G B D F# A
• CMaj7#9 = C E G B D#

Other Chords

There are also other chords which don’t exactly follow this ‘stacked thirds’ idea. These are discussed below.

• The 6th is the same note as the 13th, but it is played an octave lower and without playing the 9th or 11th. The 6th is usually used to replace to 7th in a chord.
  • C6 = C E G A (This is a substitute for a CMaj7 chord)
  • C69 = C E G A D (This is a substitute for a CMaj7 chord)
  • Cm6 = C E♭ G A (This is a substitute for a Cm7 chord)
  • Cm69 = C E♭ G A D (This is a substitute for a Cm7 chord)
• A suspended chord (or Sus chord) is a chord where the 3rd is replaced by either the 2nd or the 4th. A sus4 chord (where the 4th replaces the 3rd) is much more common than a sus2 chord. As such, you can drop the 4 in the notation as it in implied.
  • C7sus2 = C D G B♭
  • C7sus4 = C7sus = C F G B♭ (This is a substitute for a C7 chord)
• Sus chords can also be extended like any other chord. A specific type of sus chord is called a Phrygian Chord (because it is derived from the Phrygian mode). The Phrygian Chord is simply a:
  • C7sus♭9 = C F G B♭ D♭

We will be discussing Sus chords and Phrygian chords later in this module

Keys

We covered how keys work in the previous module. Nevertheless, it’s worth explicitly stating that keys work the same way with 7th chords as they do with triads. A triad is considered to be in a particular key if it only uses notes from that key/scale. Similarly, a 7th chord is considered to be in a particular key if it only uses notes from that key/scale, there is just one more note to account for. Otherwise, there is no difference.

Chords in the key of C	I	ii	iii	IV	V	vi	vii
Triads	C	Dm	Em	F	G	Am	Bo
7th Chords	CMaj7	Dm7	Em7	FMaj7	G7	Am	Bm7♭5

In Practice

So that’s the basics of Jazz Chords. If you’ve understood all that, you’re well on your way to playing Jazz already. So in conclusion:

• In Jazz we use the 7th chord as our basic chord;
• We can extend and alter the 7th chord by adding tensions (9ths, 11ths and 13ths).

When you’re playing from a lead sheet and you see the chord CMaj7, you would rarely just play a CMaj7 chord (as this sounds a bit boring). Instead you could play a CMaj9 or a CMaj13 or a CMaj13#11 or a C69 to make the chord a little bit more harmonically interesting.

However, while all tensions exist in theory, not all of them are used in practice (for example, you would never (rarely) find a CMaj7♭9♭13 chord in practice). To understand why, we need to discuss something called ‘available tensions’ which is the subject of the next lesson.

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