Altered (full)
7alt
0 - 4 - 6 - 10 - 13 - 15Dom7 b5 b9 #9 — fully altered with both 9ths
About Altered (full)
An altered dominant is a dominant seventh with every available note altered — in C that is C, E, G♭, B♭, D♭ and D♯, written C7alt. It is not one chord among many but the name of a whole approach: everything that can be raised or lowered has been, and only the two notes that make the chord a dominant are left untouched.
Notes and formula
The formula is 1 – 3 – ♭5 – ♭7 – ♭9 – ♯9, or 0 – 4 – 6 – 10 – 13 – 15 in semitones. Six notes, four of them alterations.
The third and the seventh survive because removing either would stop the chord being a dominant. Everything else — fifth, ninth, thirteenth — is fair game, and in the full form all of it has been altered at once.
The scale that defines it
The altered scale is the seventh mode of melodic minor, and this chord is simply that scale stacked in thirds. Every note of the chord belongs to it and every note of the scale is available over the chord.
That correspondence is why players talk about the chord and the scale interchangeably. Writing 7alt on a chart is a way of saying: play the altered scale and voice whatever you like from it.
How to play it
Nobody plays all six notes. The standard voicing is the third, the seventh, and two alterations chosen for voice-leading — C–E–B♭–D♯, or E–B♭–D♭–G♭ with the root in the bass.
On guitar the usual shape is x–3–2–3–4–x with the raised ninth on top, and players add or swap alterations by moving one finger.
Where it belongs
At the end of a phrase, resolving down a fifth, in bebop and everything descended from it. The more altered the dominant, the more relief the resolution provides.
It is essentially absent from music that is not jazz-derived. Four simultaneous alterations require an audience trained to hear the chord as a dominant, and outside jazz that training cannot be assumed.
How to read the symbol
C7alt does not tell you which notes to play. It tells you which notes are forbidden — the natural fifth, the natural ninth, the natural thirteenth — and leaves the rest to the player.
Charts that specify 7♯5♯9 or 7♭5♭9 are asking for a particular sound. A chart that says alt is delegating the decision, and a player who voices the same alterations every time is not reading it fully.
Scales that contain it
The altered scale, by definition. The half–whole diminished scale contains most of the same alterations but keeps a natural thirteenth, which is why the two sound related and not identical.
Whole tone contains the flattened fifth and the raised fifth but neither altered ninth, so it fits a smaller subset — useful when the chart says 7♯5 rather than alt.
Frequently asked questions
What notes are in a C7alt chord?
C, E, G♭, B♭, D♭ and D♯ in the full form. In practice players choose the third, the seventh and two alterations, and voice the rest to taste.
What does alt actually instruct?
It forbids the natural fifth, ninth and thirteenth, and leaves the choice of alterations to the player. That is why two musicians can read the same symbol and voice different chords.
Which scale goes with it?
The altered scale — the seventh mode of melodic minor. The chord is that scale stacked in thirds, which is why the two names are used interchangeably.