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<h1>Altered Scale</h1>
<p>The altered scale is the seventh mode of the melodic minor scale and the primary tool for playing over altered dominant chords (7♭9, 7♯9, 7♭13, 7♯11, and combinations). It contains every possible alteration of a dominant seventh chord simultaneously — ♭9, ♯9, ♯11, ♭13 — which makes it maximally tense and maximally suited for creating the dissonance that demands resolution to the tonic. Bill Evans, John Coltrane, and virtually every post-bop jazz musician uses it constantly over altered V7 chords.</p>

<h2>Construction</h2>
<pre>
G altered scale (7th mode of A♭ melodic minor):
G  A♭  B♭  B  D♭  E♭  F  G

Formula: 1  ♭2  ♭3  3  ♭5  ♭6  ♭7
(where 3 = major 3rd, ♭3 = minor 3rd = enharmonic ♯9)

Shortcut: the altered scale is always the melodic minor scale
starting a half step above the dominant chord root.
G altered = A♭ melodic minor (half step above G)
C altered = D♭ melodic minor (half step above C)
F altered = G♭ melodic minor (half step above F)
</pre>

<h2>What's Altered vs. Unaltered</h2>

<table>
  <thead><tr><th>Extension</th><th>G Mixolydian (unaltered)</th><th>G Altered</th><th>Status</th></tr></thead>
  <tbody>
    <tr><td>9th</td><td>A (natural 9th)</td><td>A♭ (♭9) + B♭ (♯9)</td><td>Both alterations present</td></tr>
    <tr><td>11th/4th</td><td>C (natural)</td><td>D♭ (♯11/♭5)</td><td>Tritone substitution note</td></tr>
    <tr><td>13th/6th</td><td>E (natural)</td><td>E♭ (♭13)</td><td>Altered — dark</td></tr>
    <tr><td>7th</td><td>F (♭7)</td><td>F (♭7)</td><td>Preserved — defines dominant</td></tr>
    <tr><td>3rd</td><td>B (major 3rd)</td><td>B (major 3rd)</td><td>Preserved — defines dominant</td></tr>
  </tbody>
</table>

<p>The major 3rd (B) and minor 7th (F) — the two notes that define a G dominant seventh chord — are preserved. Everything else is altered. This is why the scale sounds so tense: all the available colouring notes are pushed to their most dissonant positions, while the chord's identity is maintained.</p>

<h2>Parent Scale: Melodic Minor</h2>
<pre>
A♭ melodic minor: A♭  B♭  C♭  D♭  E♭  F  G  A♭
7th mode (start on G): G  A♭  B♭  B  D♭  E♭  F  G
                       = G altered scale

The altered scale = 7th mode of melodic minor a half step up.
</pre>

<h2>Using the Altered Scale in a ii-V-I</h2>
<pre>
Standard ii-V-I in C major:
  Dm7     → G7       → Cmaj7
  D Dorian   G Mixolydian   C Lydian / C Ionian

With altered dominant:
  Dm7      → G7alt         → Cmaj7
  D Dorian   G altered        C Lydian / C Ionian
             (A♭ melodic minor)

The altered scale creates maximum harmonic tension over G7,
which resolves completely when you land on C.
If you don't resolve convincingly, the alteration sounds arbitrary.
Resolution is the point — alteration is the setup.
</pre>

<h2>Chord Voicings for Altered Dominant</h2>

<table>
  <thead><tr><th>Voicing type</th><th>Notes (G7alt)</th><th>Character</th></tr></thead>
  <tbody>
    <tr><td>Root voicing</td><td>G B F A♭</td><td>Root, M3, ♭7, ♭9</td></tr>
    <tr><td>Rootless (jazz piano)</td><td>B F A♭ E♭</td><td>M3, ♭7, ♭9, ♭13 — rich, dense</td></tr>
    <tr><td>Shell voicing</td><td>B F E♭</td><td>M3, ♭7, ♭13 — sparse but clear</td></tr>
    <tr><td>With ♯9</td><td>G B F B♭</td><td>Root, M3, ♭7, ♯9 — the "Hendrix chord" as a dominant</td></tr>
  </tbody>
</table>

<h2>Altered vs. Lydian Dominant vs. Half-Whole Diminished</h2>

<table>
  <thead><tr><th>Scale</th><th>Over G7</th><th>Key character</th><th>Tensions</th></tr></thead>
  <tbody>
    <tr><td>G Mixolydian</td><td>G7 (unaltered)</td><td>Natural, open, bluesy</td><td>None — 9th, 11th, 13th all natural</td></tr>
    <tr><td>G Lydian dominant</td><td>G7#11</td><td>Bright, suspended, modern</td><td>♯11 only — floating, not tense</td></tr>
    <tr><td>G half-whole dim.</td><td>G7♭9, G7♯9</td><td>Tense, rich alterations</td><td>♭9, ♯9, ♯11, natural 5th and 13th</td></tr>
    <tr><td>G altered</td><td>G7alt (♭9♯9♭13)</td><td>Maximum tension, dark</td><td>♭9, ♯9, ♯11, ♭13 — everything altered</td></tr>
  </tbody>
</table>

<h2>References</h2>
<ul>
  <li>Levine — <em>The Jazz Theory Book</em></li>
  <li>Bergonzi — <em>Inside Improvisation Series</em></li>
  <li><a href="https://www.jazzguitar.be/blog/altered-scale/" target="_blank" rel="noopener">jazzguitar.be — Altered Scale ↗</a></li>
</ul>
