This tuning, which we've named C Major Sixth/Ninth Open, offers a rich and expansive sound palette suitable for various genres from alternative rock to jazz-fusion and even some modern folk styles. The open strings immediately form a beautiful C Major 6/9 chord (C-D-G-C-E-A), providing a full, resonant foundation ideal for strumming without fretting. This makes it exceptionally playable for open-string drones and creating rich harmonic textures with minimal effort.

Technically, this is a highly distinctive re-entrant tuning. The open notes are C2 D2 G3 C3 E4 A4. The most notable technical feature is the re-entrant nature between the 4th (G3) and 3rd (C3) strings, where the 3rd string is actually lower in pitch than the 4th. This creates unique voicings and melodic possibilities not found in standard linear tunings. The wide intervals between the lowest strings (C2 to D2, D2 to G3) offer a powerful, open sound that can be both heavy and resonant, while the upper strings provide bright, chimey qualities.

When played open, the full set of strings yields a rich C Major 6/9 chord. Individual string groupings also present interesting harmonies:

• Strings 6, 5, 4 (C2, D2, G3): Offers a wide, powerful low-end range with a strong C-G perfect fifth and a D second.
• Strings 4, 3, 2 (G3, C3, E4): Forms a C Major triad in an inversion (C/G), making open G, C, and E voicings easily accessible.
• Strings 3, 2, 1 (C3, E4, A4): Creates a C Major 6 chord, perfect for bright, ringing melodic passages or adding a sophisticated edge to chord progressions.

The presence of the low C and D strings provides a strong, guttural foundation for heavy riffs, while the upper strings offer bright, chimey qualities that can be leveraged for melodic leads and intricate chord work. Chords based on C will feel particularly natural, and the intervals also lend themselves well to suspended or added-tone chords with slight finger adjustments, opening up a world of creative chordal exploration.

Here are the target notes for each string in this tuning:

• 6th String (Low E): C2
• 5th String (A): D2
• 4th String (D): G3
• 3rd String (G): C3
• 2nd String (B): E4
• 1st String (High E): A4

How to Tune from Standard E:

This tuning requires significant adjustments from standard E Standard tuning (E2 A2 D3 G3 B3 E4). Please note that for string movements exceeding 4 semitones up or down, using a different string gauge is highly recommended to ensure proper tension, intonation, and to prevent string breakage or damage to your instrument. Proceed with caution, especially when tuning strings up substantially.

• 6th String (Low E to C2): Tune down 4 semitones.
• 5th String (A to D2): Tune down 7 semitones. This is a significant drop; a heavier gauge string is strongly advised.
• 4th String (D to G3): Tune up 5 semitones. This is a considerable rise; a lighter gauge string is strongly advised.
• 3rd String (G to C3): Tune down 7 semitones. This is a significant drop; a heavier gauge string is strongly advised.
• 2nd String (B to E4): Tune up 5 semitones. This is a considerable rise; a lighter gauge string is strongly advised.
• 1st String (High E to A4): Tune up 5 semitones. This is a considerable rise; a lighter gauge string is strongly advised.