Altered Chords Guitar – Complete Guide for Guitar Players

An altered chord is a seventh chord (or higher extension) with the fifth and/or ninth raised or lowered by a half-step from its natural position. A standard C7 chord contains C–E–G–Bb (root, major third, perfect fifth, minor seventh). An altered version might be C7b5 (C–E–Gb–Bb, the fifth lowered), or C7#9 (C–E–G–Bb–C#, the ninth raised), or C7b5b9 (C–E–Gb–Bb–B, both fifth and ninth altered).

Altered chords sound tense and unstable. They’re not meant to sit still; they demand resolution. In jazz, an altered dominant chord (like G7alt over a C minor progression) creates harmonic tension that resolves beautifully when the chord finally moves. In rock and pop, altered chords are rare but dramatic when they appear—think of Jimi Hendrix’s #9 chord sound, which became iconic.

The notation C7alt (with “alt” meaning “altered”) is a shorthand in jazz. It means “use some combination of raised or lowered fifths and ninths”—the exact alterations depend on the harmonic context and the improviser’s choice. There’s flexibility built into the term.

Types of alterations: b5, #5, b9, #9

The flattened fifth (b5)

Lower the perfect fifth by a half-step. In C7, the perfect fifth is G. Flatten it to Gb. C7b5 is now C–E–Gb–Bb. The flattened fifth creates a tritone interval (also called a diminished fifth) between the third (E) and the fifth (Gb). This tritone is the most dissonant interval in Western music—it’s tense and demands resolution.

C7b5 sounds dark and ominous. It pulls strongly toward resolution, usually down to the next root. In jazz, a G7b5 voicing often resolves down to Cmaj7 or Cmin7.

The sharpened fifth (#5)

Raise the perfect fifth by a half-step. In C7, raise G to G#. C7#5 is now C–E–G#–Bb. This creates a different kind of tension—a major third interval (E to G#) instead of a perfect fifth. The augmented quality (raised fifth) sounds unstable and surreal.

C7#5 also resolves downward, but it has a brighter, more surreal character than b5. It sounds futuristic or dreamlike.

The flattened ninth (b9)

Lower the major ninth by a half-step. If a standard C9 is C–E–G–Bb–D, a C7b9 is C–E–G–Bb–Db. The flattened ninth (Db, which is also called a minor second) sits just a half-step above the root, creating a distinctive grating sound. It’s dissonant and edgy.

C7b9 is also called a Phrygian dominant sound (from modal harmony). It’s common in flamenco, blues, and jazz—especially over minor or modal progressions.

The sharpened ninth (#9)

Raise the major ninth by a half-step. A C7#9 is C–E–G–Bb–C# (Db enharmonically, but written as C#). The sharpened ninth is the famous “Hendrix chord”—Jimi Hendrix popularized it on electric guitar. It sounds experimental, psychedelic, and rock-forward.

C7#9 has a distinct character: the ninth is so close to the root (just a half-step above) that it creates a clashing, dirty sound. On electric guitar with distortion or effects, C7#9 is iconic.

How to build altered chords

Start with a seventh chord (root, major third, perfect fifth, minor seventh). Then modify one or both of the upper extensions (fifth and ninth).

C7 (base chord): C–E–G–Bb
C7b5: C–E–Gb–Bb (flatten the G to Gb)
C7#5: C–E–G#–Bb (raise the G to G#)
C7b9: C–E–G–Bb–Db (add a major ninth D, then flatten it to Db)
C7#9: C–E–G–Bb–C# (add a major ninth D, then raise it to C#)
C7b5b9: C–E–Gb–Bb–Db (both fifth and ninth lowered—very tense)
C7#5#9: C–E–G#–Bb–C# (both raised—bright and dissonant)

On guitar, you don’t always need every note. You can omit the root (another instrument will provide it) or omit the fifth if space is tight. What matters is which alterations you emphasize in the voicing.

Altered chord voicings on guitar

C7b5 voicing

Emphasize the tritone (E and Gb). A three-string voicing: C (fret 3, A string), E (fret 2, D string), Gb (fret 4, G string). Strum those three and you hear the altered dominant clearly. The tritone E–Gb sits naturally on frets 2–4.

C7#5 voicing

Emphasize the raised fifth. A voicing: C (fret 3, A string), E (fret 2, D string), G# (fret 5, G string), Bb (fret 6, B string). The raised G# creates a major-third interval with the E—bright and surreal.

C7b9 voicing

Add the flattened ninth (Db) to a base C7. Voicing: C (fret 3, A string), Bb (fret 1, D string), Db (fret 1, G string). The Bb and Db are adjacent frets—they clash and grind against each other, creating the grating, edgy character.

C7#9 (Hendrix chord) voicing

The classic Hendrix voicing: low E string open (E), A string fret 3 (C), D string fret 2 (E), G string fret 4 (C#), B string fret 3 (E or similar). Or simplified: C (fret 3, A), C# (fret 4, G), E (open high E). Strum and you get that iconic clashing sound.

The C# sits one fret below D, creating a clash. This is the sound of electric guitar blues and rock distortion. Study jazz chord diagrams to see exact fingerings and positions for these and other alterations.

When and where to use altered chords

Altered chords are most at home in jazz. A jazz improviser or comping guitarist uses altered dominants (like G7alt) over V7–I progressions to create chromatic tension that resolves beautifully. The altered chord creates expectation; the resolution (to the I chord) satisfies it.

In blues, a C7b9 voicing over a minor pentatonic solo adds grit and soulfulness. The flattened ninth is essential to blues harmonic language.

In rock and metal, altered chords appear less frequently but have high impact. The Hendrix #9 is iconic. A raised or lowered fifth creates experimental, psychedelic, or heavy sounds depending on the context.

In R&B and funk, subtle alterations (like a b5 or #9) add sophistication without dominating the sound. A producer might use C7#5 or C7b9 as a color chord in a progression, creating harmonic interest without losing groove.

In pop, altered chords are rare. Pop typically uses straightforward major and minor chords. But modern pop (especially electronic or indie) sometimes borrows from jazz and uses alterations for sophistication.

Learn jazz guitar chords to understand how altered dominants function in harmony. Study seventh chords as the foundation before attempting alterations.

Altered chords in jazz context

In a jazz ii–V–I progression (in C major: Dm7–G7–Cmaj7), the V chord (G7) can be altered. A G7alt voicing (like G7b5, G7#5, or G7#9) creates tension and expectation. The ear anticipates resolution to Cmaj7.

The magic of alteration: it doesn’t change the harmonic function (G7 is still the dominant), but it adds color and urgency. The resolution feels more dramatic and satisfying.

Jazz musicians use alterations intuitively based on ear and context. A chord might be altered b5 in one progression, #9 in another. There’s no single “correct” alteration—it’s an artistic choice that depends on the emotional effect you want.

Frequently Asked Questions

Do I have to learn all altered chord voicings?

No. Start with C7b5 and C7#9—these are the most common and most useful. Once you understand how to build and voice them, adapting to other alterations becomes logical. You don’t need to memorize every possibility; you need to understand the principle.

What’s the difference between an altered chord and a diminished chord?

A diminished chord (like Cdim) has a flattened third and flattened fifth, and typically a flattened seventh (creating a diminished-seventh chord). An altered chord is a seventh chord with raised or lowered fifth and/or ninth. They create different tensions and resolutions. A Cdim and a C7b5 share the flat fifth, but they’re functionally different.

Can I play altered chords on acoustic guitar?

Yes, but they sound less dramatic than on electric. Electric guitar with effects (slight distortion, reverb, delay) brings out the tension in altered chords. On acoustic, they’re more subtle but still valid. Jazz guitarists regularly play altered chords on acoustic.

When should a beginner learn altered chords?

After mastering seventh chords and basic jazz harmony. If you’re new to guitar, focus on major, minor, and seventh chords first. Once those feel natural and you’re comfortable with jazz standards, explore alterations. Altered chords are intermediate-to-advanced harmonic concepts.

How do I hear if I’m playing an altered chord correctly?

Play the alteration prominently. For C7b5, emphasize the E (third) and Gb (flattened fifth)—they should be audible. For C7#9, the C# should cut through clearly. Listen to jazz recordings of altered dominants to train your ear. Then play along and match the sound.