What is a Seventh Chord? Building 4-part Chords

In a previous lesson on building chords, we created triads or three-note harmonies using the major scale as a basis of pitch, stacking our notes into thirds to make chords.

To give our chords more color, we can continue this process, adding a diatonic seventh above each chord’s root. This note is another third in the stack. This changes the name of the chord. For this lesson, there are two types of sevenths: one is a major seventh, just a half step away from the root (B to C in C^maj7). Another is a minor seventh, a whole step away from the root (C to D in D^-7). The following apply:

Results of Adding Sevenths

• Adding a major seventh to a major triad creates a Major 7^th Chord. (C^maj7)
• Adding a minor seventh to a major triad creates a Dominant 7^th Chord. (C⁷)
• Adding a minor seventh to a minor triad creates a Minor 7^th Chord. (C^-7)
• Adding a minor seventh to a diminished triad creates a m7♭5 Chord. (C^m7♭5)

Seventh Chords in C

Now that we’ve found all of the chords that exist within a key, we can give them a name that describes how they work without using specific note names. For instance, we can call the first chord a I^maj7, reflecting that it is a major 7^th chord and that it is built from the first degree of the key. This is called chord function. It lets us think about the chord separately from the key; we can think more about the relationships between chords and less about their specific notes.

Seventh Chord Functions

Don’t stare at this for too long

Staring at these strange diagrams on the screen for too long might give you a disease. Instead, try using a pen and paper to explain the concepts to yourself on paper, and also try playing them on the guitar.

Key tasks

1. Memorize the chord types.
   • Which chord(s) are maj7?
   • Which chord(s) are min7?
   • Which chord(s) are dom7?
   • Which chord(s) are m7♭5?


2. Memorize the chord formulas:
   • major 7^th: 1 __ __ __
   • minor 7^th: 1 __ __ __
   • dominant 7^th: 1 __ __ __
   • minor 7♭5: 1 __ __ __


3. Write out all 7 chords in the following keys:
   • F major:
     
     
   • G major:
     
     
   • E Major:
     
     
   • B♭ Major: