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42: Diatonic 7ths

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Lesson 42: Diatonic 7ths

This lesson teaches the diatonic 7th chords, which are used in the chord progressions in many songs.

Before taking this lesson, you should know:
The diatonic 7th chords are the obvious combination of two ideas: diatonic triads and 7th chords.

As you know, the diatonic triads are 3-note chords built on the scale degrees of the song's key:
  • Degrees 1, 3, 5
  • Degrees 2, 4, 6
  • Degrees 3, 5, 7
  • etc.

The diatonic 7th chords are just 4-note chords built the same way:
  • Degrees 1, 3, 5, 7
  • Degrees 2, 4, 6, 8
  • Degrees 3, 5, 7, 9
  • etc.

If you understand how we figured out the diatonic triads, then you could figure out the diatonic 7th chords yourself, so I won't go through that process here, I'll just show the results:

The Common Major-Key Diatonic 7th Chords are:

Imaj7   IIm7   IIIm7   IVmaj7   V7   VIm7
(That's "one major seven, two minor seven, three minor seven, four major seven, five seven, six minor seven".)

The Common Minor-Key Diatonic 7th Chords are:

Im7   ♭IIImaj7   IVm7   Vm7   ♭VImaj7   ♭VII7
(That's "one minor seven, flat-three major seven, four minor seven, five minor seven, flat-six major seven, flat-seven seven".)

Here are charts of these chords in the common keys:

Key Imaj7 IIm7 IIIm7 IVmaj7 V7 VIm7
A♭ major A♭maj7B♭m7 Cm7D♭maj7E♭7Fm7
A major Amaj7Bm7C♯m7 Dmaj7E7F♯m7
B♭ major B♭maj7Cm7Dm7 E♭maj7F7Gm7
B major Bmaj7C♯m7 D♯m7Emaj7F♯7G♯m7
C major Cmaj7Dm7Em7 Fmaj7G7Am7
D♭ major D♭maj7E♭m7 Fm7G♭maj7A♭7B♭m7
D major Dmaj7Em7F♯m7 Gmaj7A7Bm7
E♭ major E♭maj7Fm7Gm7 A♭maj7B♭7Cm7
E major Emaj7F♯m7 G♯m7Amaj7B7C♯m7
F major Fmaj7Gm7Am7 B♭maj7C7Dm7
F♯ major F♯maj7G♯m7 A♯m7Bmaj7C♯7D♯m7
G♭ major G♭maj7A♭m7 B♭m7C♭maj7D♭7 E♭m7
G major Gmaj7Am7Bm7 Cmaj7D7Em7

Key Im7 ♭IIImaj7 IVm7 Vm7 ♭VImaj7 ♭VII7
A minor Am7Cmaj7 Dm7Em7Fmaj7G7
B♭ minor B♭m7D♭maj7 E♭m7Fm7G♭maj7A♭7
B minor Bm7Dmaj7 Em7F♯m7Gmaj7A7
C minor Cm7E♭maj7 Fm7Gm7A♭maj7B♭7
C♯ minor C♯m7Emaj7 F♯m7G♯m7Amaj7B7
D minor Dm7Fmaj7 Gm7Am7B♭maj7C7
E♭ minor E♭m7G♭maj7 A♭m7B♭m7C♭maj7 D♭7
E minor Em7Gmaj7 Am7Bm7Cmaj7D7
F minor Fm7A♭maj7 B♭m7Cm7D♭maj7 E♭7
F♯ minor F♯m7Amaj7 Bm7C♯m7Dmaj7E7
G minor Gm7B♭maj7Cm7 Dm7E♭maj7F7
G♯ minor G♯m7Bmaj7 C♯m7D♯m7Emaj7F♯7

How These 7th Chords Are Used


Diatonic 7th chords aren't usually just thrown into a song with triads for "no reason". They're usually used one of these ways:

"Jazzy" styles. In jazz, 7th chords (and even more complicated chords) are usually used everywhere instead of triads. 7th chords are also often the usual chords in "jazzy pop" styles like soul and disco. In fact, you can make a simple "jazzy version" of a triad-based song just by changing all the diatonic triads to diatonic 7th chords.

To create a melodic line. In pop styles, an occasional 7th chord might be used because it creates a strong melodic line. This melodic line might be in the actual melody, or in the bass line, or in an inner voice in the chords. A "strong melodic line" usually means a line that either:
  • Repeats the same note; -or-
  • Ascends or descends stepwise for 3 or more notes

To explain the melody. Sometimes, the instruments are just playing a triad, but the melody is singing the 7th of the chord, and the easiest way to explain why the melody note "works with the chord" is to just say that the "analysis chord" is a 7th chord, even though the "instruments chord" is just a triad.

Exercises


You can add these activities to your writing exercises (from Lesson 2: Practicing Songwriting):
  • Practice playing them. Make a list/chart, keeping track of how fast you can play these sequences, in both major and minor keys, in every key. When you can play them all at 120 BPM, you'll know them pretty well.
  • Analyze chord progressions. Analyze the chord progressions in other people's songs, and when you find a 7th chord, see if you can explain it with one of the "reasons" above.
  • Analyze melodies. When you're analyzing melodies (see Lesson 45: Embellishing Tones), watch for when the best way to analyze a melody note is to just change the song's triad chord to a 7th chord as the "analysis chord".

Next:
See examples of diatonic 7th chords in real songs, in Hook Melodies.

Lessons

1: Introduction
2: Practicing Songwriting
3: Pitch Names
4: Letters Game
5: Sharps & Flats
6: Half-Steps & Whole-Steps
7: Steps Game
8: Scales
9: Major Scale 1-2-3
10: Major 1-2-3 Games
11: Major Scale 1-5
12: Major 1-5 Games
13: Chords: Major Triads
14: Major Triad Games
15: Minor Triads
16: Minor Triad Games
17: Major Scale 1-8
18: Major Scale Games
19: Keys
20: Roman Numeral Chords
21: Scales Above 8
22: Diatonic Triads
23: Using Diatonics
24: Tonic Function
25: Subdominant & Dominant
26: Diatonic Function Analysis
27: Natural Minor Scale
28: Natural Minor Games
29: Minor Key Triads
30: 7th Chords
31: 7ths Games
32: Suspended-4th Chords
33: Time: Beats & Measures
34: Starting a Song: Hook Chords
35: Melody: Chord Tones
36: Treble Staff
37: Treble Staff Game
38: Note Lengths
39: Tied & Dotted Notes
40: Rhythm: Rests
41: Key Signatures
42: Diatonic 7ths
43: Non-Root-Bass Chords
44: Major Pentatonic Scale
45: Embellishing Tones
46: Melody Rhythm: Rolling Stone
47: Pitch & Frequency

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