Dominant 7th chords are what harmonic motion is built on. They create tension that pulls toward resolution, and that pull is one of the most fundamental feelings in Western music. Blues, jazz, rock, pop, classical - all of them use dominant 7ths because that tension and release is so satisfying to the ear.
You've probably played a G7 in a C major song without thinking much about it. This lesson explains what's actually happening when you play it, and how to use that knowledge to make your playing more musical.
What Makes a Dominant 7th
A dominant 7th chord is a major triad with a flattened (minor) seventh added on top. Take a G major chord (G, B, D) and add an F. That's G7. The interval between B and F is what creates the characteristic tension - it's a tritone, the most dissonant interval in Western harmony, and it desperately wants to resolve.
When G7 resolves to C, the B moves up to C and the F moves down to E. Both voices move by half a step in opposite directions. That voice leading is why the resolution sounds so satisfying - it's not arbitrary, it's physics and physics don't change.
The Dominant 7th Chords You Need
The most common dominant 7ths on ukulele in standard keys:
G7C7F7A7D7E7
Start with G7, C7, and D7. These three cover the most common keys for ukulele songs. Once your fingers know them automatically, add F7 and A7.
The V7-I Resolution
The most important context for a dominant 7th is the V7-I resolution. In any key, the chord built on the fifth scale degree is the dominant. When you add a seventh to that chord and then move to the tonic (I chord), you get the strongest possible cadence in tonal music.
In the key of C: G7 resolves to C.
In the key of G: D7 resolves to G.
In the key of F: C7 resolves to F.
Practice this resolution in each key until it's automatic. Strum the V7 and let it ring, then land on the I. The sense of arrival is the whole point.
Secondary Dominants
A secondary dominant is a dominant 7th chord that resolves to a chord other than the tonic. In the key of C, D7 doesn't belong to the C major scale - but it resolves strongly to G. That makes D7 the secondary dominant of G, written as V7/V.
You don't need to remember the theory terminology. What you need to remember is this: you can put a dominant 7th chord a fifth above any chord in a progression and it will pull toward that chord with extra force. It's a tool for adding harmonic color and momentum.
Practice Exercise
Play a I-IV-V7-I progression in C: C, F, G7, C. Strum each chord four times. Listen to the G7. It's the most harmonically charged moment in the progression. The chord wants to move.
Then try inserting a secondary dominant before the IV chord: C, C7, F, G7, C. The C7 sets up the F with extra intention. That's a ii-V-I in F embedded inside a C progression.
Questions and Answers
What is a dominant 7th chord?
A dominant 7th chord is a major triad with a minor seventh added on top. It is named dominant because it is built on the fifth scale degree (the dominant) of a major scale. The chord contains a tritone interval that creates strong tension, which resolves naturally when the chord moves to the tonic chord a fifth below.
Why does G7 resolve to C?
G7 contains the notes G, B, D, and F. The B and F form a tritone - the most dissonant interval in Western harmony. When G7 moves to C, the B rises by a half step to C and the F falls by a half step to E. Both notes resolve by the smallest possible interval in opposite directions, which produces a strong sense of arrival on the C chord.
