This is a truly expansive and unique 8-string guitar tuning, diving remarkably deep into the lower registers with its foundational C1. It presents an intriguing blend of tightly stacked perfect fifths in the bass and more varied, often compact, intervals in the higher strings. The mention of this tuning within D'Addario's string tension calculator suggests a contemporary and perhaps experimental approach to extended range guitars, designed for players seeking new sonic landscapes beyond conventional tunings.

Technical Analysis

The tuning for this 8-string guitar is C1-G1-D2-A2-E3-G3-C4-D4 (from lowest to highest string). It features a distinct two-part structure:

• Lower Register (Strings 8-5): The lowest four strings (C1-G1-D2-A2) are tuned in perfect fifths. This 'quintal' stacking provides an incredibly robust, resonant, and powerful low end, reminiscent of the lower registers of 'New Standard Tuning' (NST) but starting even lower. This configuration is ideal for massive power chords, deep rhythmic riffs, and drone effects.
• Upper Register (Strings 4-1): The higher four strings (E3-G3-C4-D4) shift to a more varied and complex interval structure. The interval between E3 and G3 is a minor third (3 semitones). G3 to C4 forms a perfect fourth (5 semitones), and C4 to D4 is a major second (2 semitones). This blend of intervals creates a versatile upper range, moving away from standard guitar intervals, offering unique possibilities for melodic lines, arpeggios, and clustered chord voicings.

Open Chords & Reachable Shapes

This tuning inherently offers:

• Heavy Power Chords: The bottom five strings (C-G-D-A-E) being tuned in perfect fifths make it exceptionally easy to play full, resonant power chords across multiple strings with minimal fretting. Open C5, G5, D5, A5, and E5 power chords are readily available by simply muting higher strings.
• Unique Voicings: The combination of the 4th (E3), 3rd (G3), and 2nd (C4) strings open creates interesting harmonies like an Em7sus4 or Cmaj7/E, offering a distinct harmonic flavor.
• Dense Clusters: The closer intervals on the top three strings (G3-C4-D4) allow for tight, harmonically rich clusters that can be leveraged for modern jazz, progressive metal, or experimental soundscapes.
• Arpeggiated Possibilities: The varied intervals encourage players to explore new arpeggio patterns, moving away from familiar shapes and opening up new melodic and harmonic ideas.

How to Tune

To set up your 8-string guitar for the Deep Range CGDAEGCD tuning, adjust each string according to the following movements:

• 8th String (C1): Tune down 1 semitone.
• 7th String (G1): Tune up 1 semitone.
• 6th String (D2): Tune down 2 semitones.
• 5th String (A2): Keep as is; no change (0 semitones).
• 4th String (E3): Tune up 2 semitones.
• 3rd String (G3): Keep as is; no change (0 semitones).
• 2nd String (C4): Tune up 1 semitone.
• 1st String (D4): Tune down 2 semitones.

Important Considerations: When making tuning adjustments, always be mindful of string tension. While the individual string movements for this tuning are relatively minor (within 2 semitones), significant deviations from a guitar's previous tuning can impact playability and intonation. For tunings requiring movements exceeding 4 semitones (either up or down) from a baseline, a different string gauge is generally advised to ensure optimal performance and prevent string breakage or excessive slackness.

8th String (C1): This is your lowest string, tuned to C1, providing a profound and commanding bass foundation for the entire tuning.

7th String (G1): Tuned to G1, it forms a perfect fifth with the 8th string, contributing to a powerful and resonant low end.

6th String (D2): Set to D2, this string continues the perfect fifth interval from the 7th string, further extending the rich and deep bass range.

5th String (A2): Tuned to A2, maintaining the perfect fifth interval, completing a robust quintal stack over the four lowest strings.

4th String (E3): Tuned to E3, creating a perfect fifth with the 5th string, but also serving as a crucial transition point before the interval structure changes in the higher register.

3rd String (G3): Tuned to G3, this string forms a minor third interval with the 4th string, introducing a warmer and more compact harmonic color.

2nd String (C4): Set to C4, it is a perfect fourth above the 3rd string, offering a strong tonal center and opening up versatile melodic and chordal possibilities.

1st String (D4): This is your highest string, tuned to D4, forming a major second above the 2nd string, which concludes the tuning with a tight, often used for intricate lead work or unique chord voicings.