The GDACGCD tuning for a 7-string guitar is a rich and versatile open tuning, characterized by its deep low end and expansive harmonic possibilities. As described, it provides ready access to four distinct keys – Bb, F, C, and G – through its open strings, making it exceptionally flexible for various musical contexts, from expansive ambient soundscapes to driving heavy riffs, or even folk-inspired melodies with a modern twist.

Technical Analysis:

This tuning spans a wide range from a low G1 on the 7th string to a D4 on the 1st string. The intervals between the open strings create a complex, resonant voicing. Let's break it down:

• G1 (String 7) - D2 (String 6): Perfect Fifth (P5)
• D2 (String 6) - A2 (String 5): Perfect Fifth (P5)
• A2 (String 5) - C3 (String 4): Minor Third (m3)
• C3 (String 4) - G3 (String 3): Perfect Fifth (P5)
• G3 (String 3) - C4 (String 2): Perfect Fourth (P4)
• C4 (String 2) - D4 (String 1): Major Second (M2)

The prevalence of perfect fifths (G-D, D-A, C-G) provides a strong, foundational power-chord like sound when strummed selectively. The central C-G-C grouping (strings 4, 3, 2) forms a strong C Major triad, offering a clear tonal center. The tuning also contains a G major triad (G-D-G) across strings 7, 6, and 3, which, combined with the C major elements, creates an open Gsus2/4 or Cadd9sus2 chord when strummed entirely.

Open and Reachable Chords:

• Open Strum (All Strings): Produces a rich, resonant Gsus2add4add9 (G-D-A-C-G-C-D) or Cmaj7sus2/G, providing a full, ambiguous, and modern sound that can serve as a drone or a complex chord.
• Power Chords: The many perfect fifths make 2-string and 3-string power chords easily accessible across the neck by simply fretting two adjacent strings at the same fret, or skipping strings to use the G-D or D-A pairs.
• C Major Triad: Strings 4, 3, 2 (C3, G3, C4) naturally form an open C major chord, providing a bright, clear sound.
• G Major Triad: Strings 7, 6, 3 (G1, D2, G3) form an open G major chord, lending itself to deep, resonant G-based harmonies.
• Sus Chords: The C-G-C-D relationship on strings 4-1 naturally hints at Cmaj7sus2 or Gsus4/add9 voicings. Simple one-finger barres can easily create rich suspended chords or minor voicings by adjusting the 'A' string.
• Modal Playability: The open Bb, F, C, and G keys suggest strong potential for modal improvisation, allowing for easy transitions between these tonalities without complex chord shapes.

This tuning invites exploration, offering both powerful low-end support and intricate harmonic clusters, making it a compelling choice for guitarists looking to break free from standard voicings.

Open String Notes

• String 7: G1 (Lowest String)
• String 6: D2
• String 5: A2
• String 4: C3
• String 3: G3
• String 2: C4
• String 1: D4 (Highest String)

How to Tune

To achieve the 'GDACGCD' tuning from a standard 7-string setup (e.g., B-E-A-D-G-B-E), follow these precise adjustments for each string:

• String 7 (Lowest, target G1): Tune down 4 semitones. Please note: Tuning down 4 semitones is a significant change; consider using a heavier gauge string for optimal tension and tone.
• String 6 (target D2): Tune down 2 semitones.
• String 5 (target A2): Keep as is; no change (0 semitones).
• String 4 (target C3): Tune down 2 semitones.
• String 3 (target G3): Keep as is; no change (0 semitones).
• String 2 (target C4): Tune up 1 semitone.
• String 1 (Highest, target D4): Tune down 2 semitones.