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<h1>Ionian Mode</h1>
<p>Ionian is the major scale with a modal name. Western tonal music has been built around it for centuries. If you know your major scales, you know Ionian — the name only matters when you're talking about modes as a system and need a label for "mode 1." Understanding what makes Ionian distinct from the other major modes (Lydian, Mixolydian) sharpens your ability to choose the right sound for each chord.</p>

<h2>Construction</h2>
<pre>
The first mode of the major scale — starts on the 1st degree.
C Ionian = C major:
C D E F G A B C

Formula:      1  2  3  4  5  6  7
Step pattern: W  W  H  W  W  W  H

Half steps fall between 3–4 (E→F) and 7–1 (B→C).
These half steps create the leading tone (B pulling up to C) and the
subdominant tension (F pulling down to E).
</pre>

<h2>Ionian in Common Keys</h2>

<table>
  <thead><tr><th>Key</th><th>Ionian Notes</th><th>Characteristic notes vs. C</th></tr></thead>
  <tbody>
    <tr><td>C Ionian</td><td>C D E F G A B</td><td>No accidentals — the reference scale</td></tr>
    <tr><td>G Ionian</td><td>G A B C D E F#</td><td>F# (raised 7th of G)</td></tr>
    <tr><td>D Ionian</td><td>D E F# G A B C#</td><td>F#, C#</td></tr>
    <tr><td>F Ionian</td><td>F G A B♭ C D E</td><td>B♭ (flatted 4th of F major)</td></tr>
    <tr><td>B♭ Ionian</td><td>B♭ C D E♭ F G A</td><td>B♭, E♭</td></tr>
    <tr><td>E♭ Ionian</td><td>E♭ F G A♭ B♭ C D</td><td>B♭, E♭, A♭</td></tr>
  </tbody>
</table>

<h2>Sound and Character</h2>
<p>Bright, resolved, stable — the sound of arrival and home. When a piece of music is "in a key," Ionian is the default tonal centre. It sounds finished, comfortable, declarative. The major 7th (B in C Ionian) is the leading tone — it has a strong pull toward the tonic octave. The major 3rd (E in C Ionian) defines the "major" quality. These two intervals together are the fingerprint of Ionian.</p>

<h2>Diatonic Chords</h2>

<table>
  <thead><tr><th>Degree</th><th>Chord (C Ionian)</th><th>Quality</th><th>Function</th></tr></thead>
  <tbody>
    <tr><td>I</td><td>Cmaj7</td><td>Major 7th</td><td>Tonic — home, fully resolved</td></tr>
    <tr><td>ii</td><td>Dm7</td><td>Minor 7th</td><td>Pre-dominant</td></tr>
    <tr><td>iii</td><td>Em7</td><td>Minor 7th</td><td>Tonic substitute — shares notes with I</td></tr>
    <tr><td>IV</td><td>Fmaj7</td><td>Major 7th</td><td>Subdominant — classic contrast</td></tr>
    <tr><td>V</td><td>G7</td><td>Dominant 7th</td><td>Dominant — strongest pull to I</td></tr>
    <tr><td>vi</td><td>Am7</td><td>Minor 7th</td><td>Relative minor — tonic-like quality</td></tr>
    <tr><td>vii°</td><td>Bm7♭5</td><td>Half-diminished</td><td>Dominant function (leading tone chord)</td></tr>
  </tbody>
</table>

<h2>Ionian vs. Lydian Over Major Chords</h2>
<p>In jazz, Lydian is sometimes preferred over Ionian for tonic major chords. The reason: the perfect 4th in Ionian (F in C Ionian) creates slight tension against a Cmaj7 voicing — the F clashes with the E (major 3rd) and B (major 7th). In C Lydian the 4th is raised to F# (the tritone), which avoids this clash and gives the Lydian its characteristically open, floating quality. Outside of jazz — folk, pop, classical — Ionian is the default major sound with no caveats.</p>
<pre>
C Ionian: C D E F G A B   ← F (perfect 4th) can clash with Cmaj7
C Lydian: C D E F# G A B  ← F# (#11) adds colour without the clash

Over Cmaj7: C Lydian gives 1, 2, 3, #11, 5, 13, 7 — all usable.
Over Cmaj7: C Ionian gives 1, 2, 3, 11, 5, 13, 7 — 11 (F) is slightly tense.
</pre>

<h2>Ionian in Songwriting</h2>
<p>Major key songs that stay diatonically in Ionian have a pure, resolved quality. The moment you borrow from a parallel mode (♭VII, ♭VI, minor iv) or add secondary dominants, you're departing from pure Ionian — and that departure is exactly what creates interest and contrast. The most satisfying major key songs use Ionian as home and depart from it strategically.</p>

<h2>References</h2>
<ul>
  <li>Levine — <em>The Jazz Theory Book</em></li>
  <li>Russell — <em>Lydian Chromatic Concept of Tonal Organization</em></li>
  <li><a href="https://www.musictheory.net" target="_blank" rel="noopener">musictheory.net ↗</a></li>
</ul>
