A Diminished 7th chord is a dissonant or unstable chord and generally needs resolution. Jazz guitarists tend to play the diminished 7 or dim7 (4-note chord) instead of the diminished triad (dim) or 3 note chord. When they refer to diminished chords, they generally mean diminished 7th's.
Whenever you see the term 'diminished', it implies an interval which is one semitone less than the corresponding minor or perfect interval. Consider the following:
7 chords - tonic, 3rd, 5th, flattened 7th (1-3-5-♭7)
dim7 chords - tonic, flattened 3rd, flattened 5th, flattening an already flattened 7th (1-♭3-♭5-♭♭7)
- The chord formula for a dim7 is 1 - ♭3 - ♭5 - ♭♭7
- The symbols for a diminished 7th chord are, dim7 or º7
- The featured practice song for this session using dim7 chords is 'Love is a Losing Game' written and performed by Amy Winehouse with some excellent backing.
- For Country Music Fans we have another featured song by Patsy Cline called Crazy. It has a great melody with some very nice diminished 7 chords and a vast array of barre chords. Every learning guitarist will enjoy playing this one.
Example... Calculating C diminished 7th... Cdim7 or Cº7
- Diminished 7th chords consist of the 1st, ♭ 3rd, ♭5th and ♭♭7th notes of a Major Scale
- Remember that a minor third is equal to 3 half steps or 3 semitones.
If we move a minor third upwards from C, we get E♭...(C → C# → D → E♭).
If we move another minor 3rd upwards from E♭, we get G♭... (E♭ → E → F → G♭).
If we move another minor 3rd upwards from G♭, we get B♭♭... (G♭ → G → A♭ → B♭♭)
B♭♭ is actually an A. We call it a B♭♭ because it is the 7th note of the C diatonic scale which is B.
- Remember that all chords are based around the major scale of that chord, therefore C chords are built from the C major scale which consists of no sharps or flats. The scale reads as follows:
C - D - E - F - G - A - B - C
- Formula for a dim7 chord = 1 - ♭3 - ♭5 - ♭♭7
- Substitute the notes into the formula: 1=C, ♭3=E♭, ♭5=G♭, ♭♭7=♭♭B (A)
- Cdim7 reads as follows: C - ♭ E - ♭G - B♭♭(A)
- Simply Cdim7 = C - E♭ - G♭ - A
Dim 7 Chord Table (º7)
|♭5th||E♭||E||F♭ (E)||F||G♭||G||A♭♭ (G)||A♭|
|♭♭7th||G♭||G||A♭♭ (G)||A♭||B♭♭ (A)||B♭||C♭♭ (B♭)||C♭ (B)|
|♭3rd||F#||G♭||G||A♭||A||B♭♭ (A)||B♭||B||C♭ (B)|
|♭5th||A||B♭♭ (A)||B♭||C♭ (B)||C||D♭♭ (C)||D♭||D||E♭♭ (D)|
|♭♭7th||C||D♭♭ (C)||D♭||E♭♭ (D♭)||E♭||F♭♭ (E♭)||F♭ (E)||F||G♭♭ (F)|
Diminished 7th Chords - Right Handersdim7 OR º7
Please note that all chord charts indicate different shapes in different fret positions rather than set fret positions. Generally, there are 3 different dim7 shapes and each one can be played in 4 different positions. Let's say that you like playing the third shape, and you are looking for a Cdim7 chord... as long as the shape stays intact and any one of your 4 fingers lands on a C note, you are playing a Cdim7 chord. The same applies to the other shapes.
This also means that the same Cdim7 chord which contains the notes C-Eb-Gb-A, can also be an Ebdim7, Gbdim7 and Adim7 chord. This gives us heaps of choices. If you want to play Cdim7 and want to lead with a C note, you would play the 1st shape with the arrow representing the 11th fret, the second shape - arrow representing the 3rd fret, and the third shape with the arrow representing the 8th fret. You may want a sound that is higher up the fretboard or lower down or somewhere in between... so many flavors to choose from!