This intriguing tuning, aptly named "Open A6 or Dmaj9 tuning," offers a rich and complex sonic palette, perfect for exploring jazz, blues, and ambient soundscapes. The description "Cool tuning I found while messing around" certainly rings true, as it opens up a world of sophisticated harmonic possibilities with minimal effort.

Technical Analysis

At its core, this tuning creates a full D major 9th chord (D-F#-A-C#-E) when all open strings are strummed, making it exceptionally resonant and harmonically rich. The notes are distributed across the fretboard as follows:

• Low E String (6th): E2 (The 9th of D)
• A String (5th): A2 (The 5th of D)
• D String (4th): C#4 (The Major 7th of D)
• G String (3rd): F#4 (The Major 3rd of D)
• B String (2nd): A3 (The 5th of D, an octave higher than the 5th string)
• High E String (1st): D4 (The Root of D)

The presence of D, F#, A, C#, and E across the open strings provides a lush Dmaj9 chord, making it an excellent starting point for sophisticated progressions. The low E2 acts as the ninth, while the A2 and A3 provide a strong fifth, underpinning the chord. The C#4 and F#4 offer the critical major seventh and major third, and the D4 grounds the chord as the root.

While primarily a Dmaj9 tuning, the name "Open A6" also holds some truth. The notes A, C#, E, F# are all present within the tuning (A2, C#4, E2, F#4), allowing for an A6 chord if the D4 on the first string is omitted or used as an extension (A6add4/11). This duality provides versatility, letting you lean into either a Dmaj9 or an A6 sound depending on your strumming and fingering.

Chordal Opportunities

This tuning naturally lends itself to rich, extended chords. Simply strumming all open strings delivers a beautiful Dmaj9. Sliding a single finger across a fret will yield variations of Dmaj9 (e.g., fretting all strings at the 2nd fret would give an Emaj9). The unique distribution of pitches creates interesting voicings.

The intervals between strings offer interesting opportunities. While most intervals are ascending, the drop from the 3rd string (F#4) to the 2nd string (A3) by a minor 6th (F#4 to A3) is particularly noteworthy. This non-monotonic pitch order breaks the typical ascending pattern, creating a fascinating inner voicing that adds to the tuning's complexity and open chord sound.

The layout of the Dmaj9 chord makes it easy to find inversions and extensions by simply moving a finger or two. The presence of two A notes (A2, A3) provides a strong foundation and resonance. Chords related to D major, such as Gmaj7, Bm7, and E minor will likely find comfortable voicings. Furthermore, chords with a dominant 7th feel, such as A7 or G7, might also be interestingly voiced with simple two or three-finger shapes.

How to Tune

To achieve this rich "Open A6 or Dmaj9 tuning" from standard EADGBe tuning, follow these specific adjustments for each string:

• 6th String (Low E): Tune to E2. Keep as is; no change (0 semitones).
• 5th String (A): Tune to A2. Keep as is; no change (0 semitones).
• 4th String (D): Tune down to C#4. Tune down 1 semitone.
• 3rd String (G): Tune down to F#4. Tune down 1 semitone.
• 2nd String (B): Tune down to A3. Tune down 2 semitones.
• 1st String (High E): Tune down to D4. Tune down 2 semitones.

Please exercise caution when tuning, especially when moving strings up or down by more than a few semitones. For movements exceeding 4 semitones (either up or down), it is generally advised to consider using a different gauge string to prevent potential damage to your guitar or strings. In this particular tuning, all movements are within a safe range of 0 to 2 semitones down, so your standard string set should be perfectly suitable.

6th String (Low E): E2 (Standard E, no change)

5th String (A): A2 (Standard A, no change)

4th String (D): C#4 (Lowered from standard D)

3rd String (G): F#4 (Lowered from standard G)

2nd String (B): A3 (Lowered from standard B)

1st String (High E): D4 (Lowered from standard High E)