B Diminished
In the beginner lessons we talked about all the diatonic chords diatonic to C Major except B Diminished. Time to cover it now.
Diminished Chords are comprised of a root, its minor third, and its diminished 5th. The distance between the minor third and the diminished fifth is also minor third, so the chord is composed of 2 minor thirds and 1 diminished fifth. Diminished chords are often marked as using "dim" or °, such as Bdim, B dim, or B°.
Contents
PreReqs
Open Position B Diminished Triad
B Diminished is composed of (B D F). Although B and D occur as open strings, the common open position voicing avoids using them. The G string is typically muted, as it offers no notes from the chord until the 4th fret, which pulls us out of open position. You'll need to use your ring finger to mute the 3rd string when you strum this chord, so you don't hear the open G string.
| Root Pos. |
|---|
F ||i|-|-|-| D ||-|-|p|-| ||-|-|-|-| F ||-|-|r|-| B ||-|m|-|-| ||-|-|-|-| |
Diminished triads tend to have pretty nasty shapes, and even vanilla B dim is no different. If it's difficult, you can drop the high F with the index finger.
Harmonic Function: Leading Chord
B dim is diatonic to the key of C Major, using its 7th scale degree as the root note. Thus, it is called the vii or vii° chord. The ° indicates diminished, but you have to be careful - we are dealing with the diminished triad here, not the diminished seventh. The Diminished 7th chord has two variations - half and full. Half is indicated with a slash through the ° symbol (ø. Where the ° symbol cannot be made, such as on a standard keyboard, or to avoid ambiguity, you can use "dim" (ex. Bdim) to indicate the diminished quality of the chord.
The vii chord is called the Leading Chord. Harmonically, it has a dominant function, sharing the leading tone and 2nd of the scale with the V chord.
C F/C Bdim C I IV viio I E--0------1------1------0------ B--1------1------3------1------ G--0------2------x------0------ D--2------3------3------2------ A--3------3------2------3------ E------------------------------
Full Circle Progression
Now that we know the vii° chord, we can play the full circle progression in the key of C Major.
C F Bdim Em Am Dm G C I IV viio iii vi ii V I E-0---1---1----0---0---1---3---0-- B-1---1---3----0---1---3---3---1-- G-0---2---x----0---2---2---0---0-- D-2---3---3----2---2---0---0---2-- A-3-------2----2---0-------2---3-- E--------------0-----------3------
Diminished Fifth Interval
The vii° chord is the only diatonic chord in any major key to contain the diminished 5th interval. Remember that the most harmonic interval (other than an octave) is the perfect fifth, represented by the simple ratio of 3:2. By contrast, the diminished 5th has a ratio is 7:5. Let's see all the intervals again:
| Interval Name | Ratio |
|---|---|
| m2 | 16:15 |
| M2 | 9:8 |
| m3 | 6:5 |
| M3 | 5:4 |
| P4 | 4:3 |
| d5 | 7:5 |
| P5 | 3:2 |
| m6 | 8:5 |
| M6 | 5:3 |
| m7 | 16:9 |
| M7 | 15:8 |
As you notice, the intervals closest to the root note or octave feature the larger integer numbers for their ratios and have the largest least common multiples. Yet, the d5 is a major departure from the general trend - it appears about as harmonious as the minor 3rd and 6th, far from the perfect 4th and 5th. As it serves as the replacement of the P5 in this chord, this immediately makes the chord quite dissonant.
It's quite apparent when playing the B dim chord. This means the vii° chord not only has tension in the context of the tonality and its placement inside a progression, but it is also quite dissonant and tense in and of itself. Typically, we don't see diminished triads as frequently as 7th or other extended chords. Its half diminished (diatonic to the major, natural minor, and harmonic minor scales) variety actually adds consonance, which we will cover later.
Homework
- Know that the diminished chord is composed of root and the m3 and d5 above.
- Know that B dim consists of (B D F).
- Know that the vii° chord of a scale is a diminished chord.
- Know that the vii° chord has a dominant harmonic function.
- Practice fingering and strumming B dim in open position.
- Be sure to mute the G string.
- Practice the I - IV - vii° - I progression above.
- Practice the full circle progression above.