The notes of C7
C7 has four notes, C, E, G and B♭: E is a major 3rd above C, G is a perfect 5th above C and B♭ is a minor 7th above C. That gives the formula 1 3 5 ♭7, a major chord with a minor seventh on top.
How it sounds and where it’s used
A dominant 7th chord has a pull to it: its third and seventh are a tritone apart, an interval that wants to resolve. It’s the V7 of a key, the chord that leads home, and in the blues it’s used on I, IV and V alike for its gritty colour. You’ll meet C7 most as V7 in F major and VII7 in D minor.
- It is the V7 of F major and F minor: it pulls to F major or F minor. Its third, E, rises a half step to F, and its 7th, B♭, falls to A (A♭ in minor).
- Without its root, its three upper notes, E, G and B♭, make E diminished.
Fingering
With four notes, the outer fingers take the outside notes and the two notes a second apart (the 7th and the root, side by side) go to neighbouring fingers. In 3rd inversion the right thumb lands on a black key: move the whole hand a little further in towards the fallboard, so the fingers on white keys stay on them.
| Position | Notes | Right hand | Left hand |
|---|---|---|---|
| Root position | C E G B♭ | 1-2-3-5 | 5-3-2-1 |
| 1st inversion | E G B♭ C | 1-2-4-5 | 5-3-2-1 |
| 2nd inversion | G B♭ C E | 1-2-3-5 | 5-3-2-1 |
| 3rd inversion | B♭ C E G | 1-2-3-5 | 5-4-2-1 |
Fingers count from the thumb (1) to the little finger (5). Shown low to high, so the left hand starts with 5.
Inversions
The same four notes can be stacked with any of them lowest. 1st inversion puts the third at the bottom: E, G, B♭ and C, written C7/E. 2nd inversion puts the fifth at the bottom: G, B♭, C and E, written C7/G. 3rd inversion puts the seventh at the bottom: B♭, C, E and G, written C7/B♭. Whatever is on top, the chord is still C7: the lowest note only changes its colour. Pianists choose the position that is nearest to the chord before, so the hand moves by a step instead of jumping.
Keys with C7
C7 is built from the notes of these keys, where it is the chord on the degree shown:
A key marked harmonic minor uses the raised 7th of that minor scale, as minor-key music does for its V and vii° chords.
Finding it fast
Play C major, then add the note a whole step below C, an octave up: B♭. In root position its keys are white, white, white, black. F7 has the same shape on the keys, so learn them together.
To read it on the page as quickly, practise the shapes with the chord reading quiz, and see how the notes are counted in intervals.