Part 5: Understand the chords you already hold · Lesson 045 / 117
A diminished triad changes the fifth too
Build one diminished example after the major/minor comparison is familiar.
A diminished triad has a minor third and a diminished fifth above its root: 1–b3–b5. The diminished fifth is six semitones, one less than a perfect fifth.
Build B–D–F. B to D is a minor third, three semitones. B to F is a diminished fifth, six. The result is B diminished, written Bdim or B°. These notes will appear naturally when we build the chord family of C major.
Compare B minor, B–D–F#, with B diminished, B–D–F. The third remains minor; only the fifth changes in that comparison. This follows the same “hold most ingredients, change one” approach as your earlier chord lessons.
Use separate notes rather than forcing an unfamiliar grip. On the top strings, G-string fret 4 is B, B-string fret 3 is D, and high E fret 1 is F. Inspect them slowly.
Hear it
Diminished
Audio fileFour-beat count-in · 60 BPM · Warm sampled electric guitar. Listen once before playing along.
A concrete example
B minor = B–D–F#. B diminished = B–D–F. Lowering F# to F changes the perfect fifth into a diminished fifth.
Fretboard view
Tap a labelled note to hear it. High E/string 1 is at the top, matching tablature.
Use this as a note map, not a speed test. Once the relationships make sense, play them without looking.
Try it, slowly
- Play B–D and confirm the minor third.
- Compare F# and F above the same B.
- Play B–D–F as an arpeggio and name the two intervals from B.
Check one idea
Is every minor triad diminished?
Show the explanation
No. A minor triad has a perfect fifth. A diminished triad has a lowered, diminished fifth as well as a minor third.
A good place to stop
You can explain Bdim from its intervals without needing to memorise many diminished grips.
Return to the example after a short break. A clear explanation matters more than speed.