Chord Alterations

Chord alterations are chromatically raised or lowered 9ths and 5ths — ♭9, ♯9, ♭5/♯11, ♯5/♭13 — layered onto a Dominant Seventh Chord to make its pull toward resolution even stronger. Where a plain extension like a 9 or 13 colors a chord without changing its function, an alteration bends that extension a half-step off its diatonic home, adding dissonance that has nowhere to go but down into the next chord. The result is the sound of maximum tension right before release — the harmonic equivalent of a held breath.

Why only the dominant gets altered

A dominant chord’s job is to create instability that resolves — that’s Dominant Resolution and Tension and Release in a nutshell. The root, major 3rd, and minor 7th of a V7 are the load-bearing Chord Tones that define its function and are never touched. Alterations only ever modify the 5th and 9th, because those are the notes with no fixed job — they’re free to be pushed chromatically to intensify the chord without breaking its identity. That’s also why alterations rarely show up on major 7th or plain minor 7th chords: those chords aren’t reaching toward anywhere, so there’s nothing to intensify.

Spelling the alterations and where they resolve

Every altered tone resolves by half-step, almost always downward, into a chord tone of the target chord. In C major, off G7 resolving to Cmaj7:

• G7♭9 = G–B–D–F–A♭ → A♭ falls to G, the root of Cmaj7
• G7♯9 = G–B–D–F–A♯ → A♯ falls to A (or is heard against the 3rd, a blues-flavored clash)
• G7♯11 (=♭5) = G–B–D–F–C♯ → C♯ falls to C, the root
• G7♯5 (=♭13) = G–B–D♯–F → D♯ falls to D, the 9th of Cmaj7, or down further to C

Each alteration resolving down by half-step into the Cmaj7 that follows:

The same shapes transpose cleanly to any key. In F major, off C7 → Fmaj7:

• C7♭9 = C–E–G–B♭–D♭
• C7♯9 = C–E–G–B♭–D♯ (this ♯9, sometimes written enharmonically as E♭ and called a ♭10, is the classic funky/bluesy dominant sound)

In B♭ major, off F7 → B♭maj7: F7♯9 = F–A–C–E♭–G♯, and F7♯11 = F–A–C–E♭–B (natural 5th kept, ♯11 added above it). In E♭ major, off B♭7 → E♭maj7: B♭7♭9 = B♭–D–F–A♭–C♭.

The enharmonic pairs and the “alt” shortcut

♭5 and ♯11 are the same pitch, and so are ♯5 and ♭13 — see Enharmonic Equivalence. Jazz notation picks the spelling that reflects how the note behaves in Voice Leading: call it ♯11 when it sits above a normal perfect 5th in the voicing, ♭5 when it replaces the 5th outright; call it ♭13 when it’s heard descending toward the tonic, ♯5 when it’s built as a raised triad tone. When a chart just says “G7alt,” it means pull from The Altered Scale — the 7th mode of The Melodic Minor Scale a half-step above the root (G7alt uses A♭ melodic minor) — which stacks ♭9, ♯9, ♯11, and ♭13 all at once. You don’t have to play all four; “alt” tells the soloist “use the altered-scale sound,” not “cram in everything.”

This is the sound described more fully in The Altered Dominant, and it’s one of the standard Available Tensions a player reaches for once a plain dominant feels too tame. Altered dominants also pair naturally with Tritone Substitution and turn up constantly resolving into The Minor ii-V-i, where a chord like F7♯9♭13 leans hard into Cm7♭5 territory before landing home; comping pianists often voice these as Rootless Voicings or stack an upper-structure triad to bring out the altered color cleanly.

♫ Listen

• Miles Davis — “All Blues” (Kind of Blue, 1959): on the V chord of this 6/8 blues in G, the band slides D7♯9 up to E♭7♯9 and back — that raised-ninth clash against the major 3rd is the quintessential “blues alteration” sound, audible at the end of every chorus.
• Bill Evans Trio — “Waltz for Debby” (Waltz for Debby, 1961): listen to Evans’ left-hand voicings under the turnarounds, where ♯11 and ♯5 alterations color the dominants without ever losing the tune’s lyricism — a good model for how alterations serve the melody rather than showing off.

Related: Chord Extensions, The Tritone, Chord Symbols