Lesson 32 · All 12 keys

Dominant 9th Chord Trainer

Learn how a Dominant 9th chord is built one semitone-count at a time — a plain dominant 7th chord (Lesson 13) with a 9th stacked on top — then put it to work with three MIDI exercises: playing all 12 Dominant 9th chords around the circle of fourths, and 5 jazz plus 5 gospel chord progressions that show off its color, in every key.

How a Dominant 9th chord is built

A Dominant 9th chord — written 9 (e.g. C9) — is a 5-note chord: a plain dominant 7th chord (Lesson 13) with a 9th stacked on top. Every 9 chord — in any of the 12 keys — is built the exact same way, by counting semitones to the right from a root note:

  1. The starting note — this note names the chord.
  2. Count 4 semitones up from the root — the major 3rd.
  3. Count 3 more semitones up from the 3rd (7 semitones from the root) — the perfect 5th.
  4. Count 3 more semitones up from the 5th (10 semitones from the root) — the minor 7th, the same 7th a plain dominant 7th chord uses.
  5. Count 4 more semitones up from the 7th (14 semitones from the root — an octave plus a major 2nd) — the 9th, stacked on top of a complete dominant 7th chord.
Example — G9: start on G, count 4 semitones right to reach B, 3 more to reach D, 3 more to reach F, then 4 more to reach A (an octave and a step above the root). G‑B‑D‑F‑A is the G9 chord. The pattern 4, 3, 3, 4 (14 semitones total from root to top) is what makes a chord a "9th chord" — every one of the 12 dominant 9th chords is this same shape, just moved to start on a different key.
A dominant 9th chord still contains the full dominant 7th chord underneath (root, 3rd, 5th, ♭7th) — it just adds a bright 9th on top. That's different from an add9 chord (Lesson 26), which has no 7th at all. Because it keeps the ♭7th, a dominant 9th chord still pulls strongly toward its tonic, exactly like a plain dominant 7th chord does — the 9th just smooths and brightens the color along the way.

Try it: pick a root and build the chord step by step

Step 1 of 5
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Chord toneNoteSemitones from rootMIDI #

All 12 Dominant 9th chords at a glance

ChordRoot+4 semitones → Major 3rd+3 semitones → Perfect 5th+3 semitones → Minor 7th+4 semitones → 9th

This MIDI exercise plays all 12 Dominant 9th chords, one after another, moving around the circle of fourths — each chord's root sits a perfect 4th (5 semitones) above the last one: C → F → B♭ → E♭ → A♭ → D♭ → G♭/F♯ → B → E → A → D → G → back to C. Every chord is played as a full 5-note Dominant 9th chord (root, major 3rd, perfect 5th, minor 7th, 9th together).

Chord 1 of 12
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The 12 chords, in circle-of-fourths order

#ChordRootMajor 3rdPerfect 5thMinor 7th9th

Five jazz chord progressions built around the Dominant 9th chord. Pick a progression and play it in one key or cycle through all 12.

Key of C
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Progression in C

DegreeChordNotes

Five gospel chord progressions built around the Dominant 9th chord. Pick a progression and play it in one key or cycle through all 12.

Key of C
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Progression in C

DegreeChordNotes